Free bingo games online are not a new thing, but the way it is used to promote a site and reward loyal members is quite new. Years ago, online sites offered free bingo games, but this was along the lines of playing in fun mode, where no cash was won. That has all changed with the new model, which offers these titles with real cash money in the prize pot, with games available 24/7. Simon Collins (Managing Director of Cashcade) is credited with this innovation. Now there are many sites offering 24/7 free models.
The beauty is that even land based halls are using this as a promotional tool now. This could be in the form of a certain amount of hours of free use during the course of a day, or as a special promotion where only depositors of that week are allowed to play. Taking a look at sites which offer free bingo games, people have found that this financial model has changed the industry completely. Now, if a site doesn't offer cash-less versions of the game with real prizes, it isn't worth bothering with. There are many sites who are happy to give away real prizes in return for members' loyalty.
Any site that appeals to you should have open play available. Some offer this in the form of scratchies or other things like a Treasure Map, where participants have to play for an entire week to qualify, and members are required to spend a small amount in the preceding week. In the Treasure Map scenario, participants are then allowed to play free bingo games every day for a week and can win up to $500!
Bonuses are often given to users who register with a site, and they may or may not be forthcoming with a deposit having to be made. In other words, some sites offer a no-deposit bingo bonus. Others give a cash match on first deposits that can only be used to buy bingo tickets. These bonuses can also be earned by collecting loyalty points and redeeming them for cash, or for referring friends to a site, or for participating in chat games, tourneys, teams, and many other promotional features.