If you have a Flash/ActionScript background, I recommend checking out Ansca Mobile's Corona. It's a (commercial with free trial) Lua programming environment (including device simulator and Lua debugger) that can generate iOS and Android apps.
Corona's media and physics libraries are a great match for 2D games. Other types of apps would be more difficult.
I have no vested interest in Corona; as an ex-Flash guy, I just think it's really cool!
And an open source alternative I just discovered here on HN a week or so ago is Moai: http://getmoai.com Also Lua, also with media & physics libraries.
Corona's media and physics libraries are a great match for 2D games. Other types of apps would be more difficult.
I have no vested interest in Corona; as an ex-Flash guy, I just think it's really cool!
http://www.anscamobile.com/corona/