In 2007 the Commodore 64 has celebrated its 25 years anniversary. In 2008 you only need an internet browser and Java or Flash to enjoy pure computer nostalgia. I remember that when I was a 13 years old boy I always entered some BASIC program on a demo machine in electro stores.
FC64 Flash Commodore C64 Emulator
JaC64 Java Commodore 64 Emulator (with cool Bonzai demo “Bonzieed” playing)
c64s.com classic Commodore 64 games online! (Tetris playing)
JSIDPlay the Java SID player with the whole HVSC SID Collection!
TIP If you want to listen a good example then listen to Ouwehand_Reyn/Last_Ninja_3.sid