The site z5 give also has a lot of downloads for lots of classic 8 bit and 16 bit computers.including ppc amigas
Yep, it is the biggest demodatabase on the web and the best website on demos, for all platforms.
There is a new thing getting more and more attention, and that is demos on all sort of mobile stuff like nokia phones, pocket pc, gba, ...
Some of the stuff released on those platforms is really amazing. And you see some very famous groups returning to those platforms (CNCD, komplex, ...).
If you want to see some of this stuff, then there are gba emulators (for example Virtual gameboy on pc) and check out this gba demo:
Phloam/Unique