Work on the free software projects I keep wanting to then being too burned out from the work that pays the bills to do anything with. SBCL could use a good graphics toolkit and editing environment. Free graphics and audio production software all need more love, as does CAD. It still baffles me that the free 3d graphics package that won is Blender, when enough users want Houdini to make it a successful commercial product.

A computer algebra system that could work with hand-written expressions, for tablets and those interactive whiteboard things, would be very handy. Axiom and Reduce would both be decent CASes to build on, are free software, and would benefit from having a decent environment built on them.

I keep thinking it's a shame that these great communities form around extending videogames, then fall apart after a few years when they're no longer the cool new thing, and it would be nice to have a free platform that could be kept graphically modern for people who want to do things with games but don't want to build one from the ground up. There have been attempts to do things like that in the past, but they're either deliberately primitive to limit their scope or never reach a usable state because they're too ambitious for a hobby project.

FreeNet seems to be dead and without successors, which is a shame because it or something like it would be better than Tor hidden services for some applications.