Blue Flame Cafe - An online encyclopedia of the the blues
Classic TV Themes List - An outstanding reference of themes from TV shows prior to 1965. A must for TV Land fans!
The Space Age Pop Music Page - A fantastic reference for lovers of classic Ultra-Lounge music. Also some good info on TV and film composers.
Red Hot Jazz Archive - An exhaustive encyclopedia on jazz before 1930
Traditional Jazz (Dixieland) - HQ of the Dixieland Jazz Mailing List (DJML) with links to groups around the world. An outstanding hub site.
The Woodwind Fingering Guide - A fantastic reference on woodwind fingerings of all kinds.