[megalottachoc]

xdude.com - flash site. Even though it was small by today's standards, it had some pretty handy info for MIDI and sound processing.

Winamp.com (from the 2.x days) was also full of useful stuff. The plugin architecture meant that you could make Winamp2 do just about anything with av files. Including DJ'ing and video playlists.

Those two and Geocities.