Alfred beat me to posting my own content :)
We recently asked a number of students to use Popfly and submit a Popfly creation (a mash-up or a game). 10 of the games that were created were picked by the Popfly Team in the Games We Love http://popflywiki.com/GamesWeLove.ashx entry in the Popfly wiki.
I've embedded a couple games so you can try them out. The other links are at the bottom … beware … these games are fun!
http://www.popfly.com/users/mtaipan/theGunner
http://www.popfly.com/users/solidcell/Move%20It
http://www.popfly.com/users/karafong/ChickyBang
http://www.popfly.com/users/Dauble2k5/Shoot%20for%20the%20Stars
http://www.popfly.com/users/sachint/Demon%20Attack
http://www.popfly.com/users/hcnguyen88/ninjaDuel
http://www.popfly.com/users/Borealid/Bouncing%20Babies
http://www.popfly.com/users/dinko628/football
http://www.popfly.com/users/DarkStarX1/Alien%20Invaders