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!