Triple Town is an addictive, city-as-a-garden match three Facebook game designed by Danc of Lost Garden and Spry Fox.

The game was originally released on the Kindle as a kind of experiment to see if you could make a game on there. (you can, although there are some pretty extreme graphical limitations)  The Facebook iteration is pretty nifty.  The presentation is excellent and fun, but it's really the game mechanics that do it for me.