PlayFirst (Diner Dash authors, besides other stuff) opened their SDK for free use for game creation. The most impressive stuff about this SDK that games can be run on PC, Mac AND web browser without touching the code at all and supports whole stuff that required by such publishers as AOL.com and MSN zone (really good for widespreading the game). More nice (for developer) than PopCup SDK, Lua inside, etc. Besides that they are promising console cross-platformity as well.
Worth a look.
http://developer.playfirst.com/