I’ll use my standard tool set

Language: C++, my base code can be found here.

IDE: Visual Studio 2008 Express Edition.

Libraries: FLTK, OpenGL, OpenAL, mpg123.

For GFX: MSPaint, Gimp.

For SFX: PXTone, sfxr/Bfxr.

Possible I’ll use Tiled Editor and Bosca Seoil.

Also it’s possible (depending on the theme) I’ll drop all this and will use JS+HTML5+Canvas and will write all code from scratch. Unfortunately I’ll be a bit busy this weekend (because of really unexpected events), so this 48 hour compo actually will be 8-10 hours compo for me. But I hope I’ll have enough of time to make something minimalistic.

BTW, I’ve really improved my game from LD31 The Legend of Adlez: Knil’s Adventure. There is a small gameplay video:

Ludum Dare page of the game is here.