Fender, bass and guitar manufacturer.
Modulus Graphite, makers of basses and guitars. This archive contains pictures of their gear along with prices (in the US) etc.
Tobias Basses, again another famous bass manufacturer.
Kaman Music, the US distributors of Trace Elliot, Dean Markley, Hamer, Ovation, Takamine etc.....
SWR Engineering Inc., manufacturer of bass amps and cabs. They also have an Anonymous FTP site
La Bella, manufacturer of strings.
Thomastik-Infeld, Vienna, Austrian string manufacturer.
Aguilar Amplification (Tube bass preamp).
Washburn, bass and guitar manufacturer.
Sadowsky Basses.
Peavey, bass, amp, effects, guitar, keyboard etc. manufacturer.
Vintage Guitar magazine is the pre-eminent resource for people who buy, sell and trade vintage instruments and should be quite helpful.
Crate Amplifiers, manufacturer of bass amps and cabs. 
Super Sensitive, manufacturer of strings.
Elderly Instruments, vintage and new gear
David Gage String Shop - Home of "The Realist" acoustic bass pickup - the finest most realistic pickup that I know .
Roger Stowers KAY BASS Information page (and rifle and shotguns) - he helped date my 3/4 - 5 string. (1940)
Bob Gullihur's Double Bass Links - more links than you'll ever need!
Active Bass.com - a must for ANY bass player
Jazz Weekly - Creative Music and other forms of Avant-Guarde
Pirastro Music - Rosin and Strings
Kolstein Music - Strings, rosin, parts, auction instruments and more
Welcome to Hippyland! -This site is dedicated to the hippie in all of us.  Hippies young and old will find a very active community here
George, my bandleader has his own website too.
Dr. Bob (Keyboard from CTR's "The Band") has his own site.

Here are some Jazz Links

All About Jazz
Contemporary jazz.com
Jazz Online
Jazz Review
Jazz Corner
NetBeat