FarmVille on Facebook (http://farmville.com)

This new viral Facebook game has attracted 66 million monthly users in early beta and for good reason. It's really, really fun. Players start out small with a few plots tended by an overalled avatar that walks down the rows and uses a hoe.  Harvesting crops, which take from two hours to four days to grow, earn experience points, which in turn unlock more farm objects for purchase. Bit by bit, players create sprawling properties studded with mooing cows, blossoming fruit trees, quaint farmhouses and acres of thriving crops such as juicy strawberries and golden wheat fields. FarmVille's semi-automatic (you can cancel them) Facebook updates will annoy friends who aren’t farmers. And the game's not really free; the special points needed to fully outfit a farm are so hard to earn you almost have to pull out a credit card. But the game is mesmerizing and hard to abandon.

Online interaction: Fellow players are Facebook friends. Players can visit each other's farms and leave short messages, which are indicated onscreen as cute signposts. Offensive messages can be reported to moderators. Players can also ask each other to help out, such as raking leaves or shooing away foxes, but these are canned messages generated by the system. The game has a message board, which we found to be a mostly helpful and civil exchange of tips.