All you need these days is Wikipedia and Google. However, here’s a few worth a visit.....
Music Styles
Early Recorded Sounds and Wax Cylinders
Music Reference
http://www.robertchristgau.com/
Great sites that don't fit into any category
James Randi - Sceptic or Troublemaker? You decide
Radio
There's episode guides, listings, and details for almost all the speech based BBC radio programmes (or programs if you like) from 1997 onwards, with a substantial amount of stuff before that year, and a small smattering of non BBC programmes.
Friends of mine
My brother's website - You sampled my cheese, now try Harvey's chalk....