C64?
Just head over to [link deleted] and download all your old favorites.
Need to get them back onto your actual C64 hardware? Just check out their FAQ. You can even convert the downloads into audio files and play them from your computer/ipod into your C64's cassette input.
Don't have a C64 laying around? Grab an
emulator.
The lesson is that if the hardware / data format is popular enough to be in widespread use at any time, the chances are pretty high that you'll still be able to access it well into the future.
Moderator note: I'm afraid we've had to remove the web site URL. It contains copyrighted software which they are hosting without permission of the copyright holder, and MR's rules prohibit linking to such a site. Sorry!