Here's some good starting points, if your want to revive your youth (like I did):
- C64 Portal - a portal with lots of news and information. The C64 scene is still alive!
- Project 64 - collection of manuals and documentation. Your precious Programmers Reference Guide can stay in the vault...
- C64 Unlimited - an archive of games and applications (although the application section is still empty).
- Small VI Clone for the Commodore 64 - the classic UNIX editor, vi. Works like a charm... now how about a port of GNU/Emacs?
- cc65 - a freeware C compiler for 6502 based systems. This is neat. It's actually a cross-compiler, so you can develop and compile a program on your PC. Has a C64 specific library.
- LUnix - a little UNIX for Commodore 64. I haven't tried it (yet). Promises preemptive multitasking!
Long live the C64!