This could be pretty fun! I may join in if I can find the time (have to squeeze it in with my job).
Last 'game jam' (wasn't actually organised or planned) I worked on went really well! We managed to make a game in 12 days for a deadline -- long story -- that we based off a weird mix of Geometry Wars and Typing of the Dead. Designed for a controller but also plays nicely on tablets too! Looks like this: https://www.dropbox.com/s/h6iza29g423h8sn/screenshot_1.png
I'm going to put up a blog post about it soon and possibly just release the PC version on there for free. Works very nicely with Adobe AIR's gamepad support as of version 3.8.
If I do join in, I'll likely be using AS3 / Flex in FlashDevelop with a Stage3D modified version of the Flashpunk library.
Edit: Also, neon purple.