Here are a few popular ones to name.

Full Tilt Poker
Sportsbook Poker
Doyles Room
PDC Poker
Titan Poker
Absolute Poker

There are many, many more, but heres a few to get your feet wet.

If you are going to compare a freeroll tournament to a normal buy in tournament, the winnings at a freeroll tournament are going to be lower and in case you have already managed gain some skills to play at an online poker tournament you should go for the paid ones since the winnings are consistently higher.
Many online poker rooms out there offer freeroll tournaments. In case you are after freerolls, you just have to visit the promotions section on the most popular online poker rooms and you will get the chance to find plenty of information available about the tournaments offered.

However before joining make sure that you read exactly what are the terms and conditions of joining that freeroll. This way you will be leaving out all the misinformation that you might have about that freeroll. Also, make sure you can receive a deposit bonus and rakeback at the online poker room you join. For example, you can receive carbon poker rakeback, deposit bonus, and 14 days entry into the daily first time depositors $500 Freeroll.

In the long run however these negatives are far outweighed by the long term difference made by saving money during the time you would normally be getting schooled at the tables.

1) Playing poker without risking real money. For more cautious people, freerolls are a great way to play poker without the risk of losing own money. This is also a great way to start building up your online poker bankroll without having to cash real money in. Winning one major freeroll provides you with enough money to start playing some larger tournaments with the chance of cashing out a significant sum.

2) Theres no need for bankroll management: Following a proper bankroll management (BRM) is a key factor to consider when playing for real money. A lot of players go broke because they fail to follow the BRM guidelines. When you play freerolls, you play tournaments for free. Therefore, you can ignore bankroll management.

3) Bad competition: The level and competence of the players playing freerolls is generally very low. Even if you have only limited knowledge of poker strategies, you are at an advantage compared to the majority of the freerollers, who might not even have heard of “poker odds” or “starting hand charts”. Freerolls are the fishiest poker games in the Internet!

4) Learning how to play online poker: Freerolls are a great way to familiarize yourself with playing poker online. If you don’t know the poker rules by heart, these free tournaments are great for practicing the rules. And even if you know the poker rules, freerolls are a good way to practice playing tournaments.

5) Its a good way to getting familiar with a new poker room. Every online poker site has slightly different software. The layout varies, you might need some time to find and configure your own preferred design and size of the poker tables, and keyboard shortcuts might be programmed differently to your previous poker room. Before risking your real money poker dollars, playing a few freerolls might be a good idea to find one that is to your liking.

Learning the game: If you have always desired to learn poker game with real chips and real players, poker freerolls are meant for you. You can learn about the basic rules of this game and get familiar with most desirable winning strategies associated with it. Thus, no more boring tutorials for learning poker, as freeroll tournaments can help you better. What better possible way to learn the game without risking anything?

In freeroll tournaments the quality of the game is much superior to play-money games. Players can actually win something and will therefore think twice before they make a move. In other words, play-money games are just card games while freeroll tournaments are real poker. Many players who are desperately trying to win a roll so they can get back into the game participate in these games. In order to find the best freeroll tournaments with the biggest prize pools and most participants I recommend that you visit the poker rooms with the best freerolls, and give yourself a chance to improve your poker skills, and if you are lucky, build yourself a bankroll.

If you are fortunate enough to get to the final table, chip stack size and aggressive play are the major keys to final table strategy. Revealing articles on how to win freeroll and low buyin multi table online poker tournaments conclude by breaking down a strategy based on the size of your stack and the number of players, and includes working methods on how to hammer your opponent in heads up play.

The Learning Experience

Some of the poker rooms will let you play free poker online, but only allow you to use play money with no real cash to be won. While these games are risk free, it doesn’t exactly make an optimal place to learn poker or to improve your skills. What makes online poker freerolls a better place to learn poker skills than the play money games? The integrity of play improves when there is real money to be won. When players are playing with play money, it is much easier to push all-in regardless of the hand they are holding. There’s no risk of losing money, so some players just push all their chips in to see if they can possibly catch anything. The problem with using these types of games as a learning tool is that even though you may be adapting a winning strategy, the other players will continue to just push all-in with virtually every solitary hand.

When there is money at stake, it makes it more like real poker and not just a simple card game. The players will concentrate more on winning when there is money to be won and not be so quick to go all-in on every hand. This also makes freerolls more of a quality game of poker where you can sharpen your poker skills properly and win real money at the same time.

Real Money Games

A few of the most famous online poker rooms offering online poker freerolls are Full Tilt Poker, Party Poker and Poker Stars. Full Tilt Poker has daily freerolls that are open to all and have built an excellent reputation since they began in 2004. Their very own Chris Ferguson completed a self imposed challenge of turning a bankroll of zero into $10,000, so that proves that it can be done. An equally famous poker room that offers online poker freerolls is Party Poker. They have a significant player volume and offer a softer competition that would be great for gaining skills. Poker Stars is another great poker site that offers freerolls and they have sort of a mix of competition levels. Some tables may have play that’s soft and loose, and then there are other tables with very aggressive play. Full Tilt and Poker Stars are both open to US participants, but Party Poker is not.

Whether you are a new poker player or an expert player, one of the best ways to sharpen your skills without risking any of your own money is to participate in online poker freerolls. The opportunity could be the answer for when you are looking to build a good size bankroll online without risking a dime of your own money. Visit Onlinefreerolls.com periodically for updates and reviews of the best freerolls. You can improve your skills in poker and if you are one of the lucky ones, you can build yourself a nice bankroll before you hit the high stakes tables.

Full Tilt Poker

Full Tilt Poker has been climbing in popularity since they began in 2004 and continue to be one of the leaders in the poker industry. They run freerolls of all game varieties, No-Limit Holdem, Pot-Limit Omaha, Razz and HORSE. This gives the player an option to try various games without a risk of damaging their bankroll. Most of the tournaments have cash prizes for the best 1% in the field. For larger prizes, Full Tilt has many big ticket freerolls where you can win entrance into events of WPT, WSOP, EPT and even more.

Party Poker

Party Poker is a great place for international players of all skill levels and is known for a soft and relatively loose play. The freeroll spread is among the best, with special new player events, special points promotions and country-specific freerolls. They moved away from the United States market in 2006, but have made an incredible comeback in international popularity in the last few years. A recent upgrade to the software and new player bonuses, along with the online poker freerolls make this poker site an excellent choice in which to become familiar.

Poker Stars

Poker Stars have an unmatched overall quality of tournament and game offerings that welcome players from the US. As of 2007, they have been slated as the largest of the online poker rooms with more simultaneous players online than other sites. Almost 200,000 players at a time are easily drawn to the special promotions, online freerolls and their Frequent Player Points (FPP) program. The customizable software is top of the line, too, with multi-table play, easy banking and an enormous amount of ring game traffic. With a variety of players with varying skill levels, players can choose from many different ring games, online freerolls or tournaments.

Absolute Poker and UB

Absolute Poker and Ultimate Bet Poker (now UB) joined forces in 2008 to form CEREUS Poker Network, which has proven to be an excellent choice for both. Gaining popularity and re-gaining trust hasn’t been overnight for either of the poker sites, but with the improvements in banking options, enhanced software with very nice graphics and free tournaments, like the $10,000 seasonal freerolls, the future is looking bright for both. Absolute Poker now has an impressive weekend tournament guarantee of a $500k total, since the merge with CEREUS.  The online poker freerolls that both sites offer will give an adequate avenue to learn poker and improve your skill level, along with providing an exceptional overall playing experience. Both are open to US players, as well.