I also still have a working C64 although thanks to emulators I don't need to get it out any more. You can download plenty of free C64 emulators (just Google them to find them) for Mac or PC (PC users - CCS64 or WinVice are both good) and you can download just about any game ever made for C64 at
www.c64.com. I'm a closet C64 nut, even after all these years and in the age of the floating point processing, realtime particle physics scattering and dynamic environment mapping on PS3 game graphics, I STILL love playing really old games! You just cannot beat the purity of the fun of these old games.
You can now buy a C64 emulator for the iPod / iPad / iPhone too but I don't think this is very good because of the tricky control methods.
I also have a few fuzzy memories of Compunet, a very early precursor to the Internet. It was a C64 network which allowed you to sit your old dial phone onto an acoustic modem and let you download 8-bit artwork and game cheats. It took forever to download a mere 28k, but it was exciting and a very prescient view of the future.