Since no one has mentioned it yet on here, i figured i would.
http: //code . google . com / android /
Features of the iphone, touch screens, accelerated 3D graphics (Quake on a phone), and its OPEN SOURCE and easy as **** for developers. It took me all of about 5 minutes to create a hello world app and run in the emulator, from download to install of sdk/eclipse plugin to development. Has anyone else checked this out?