valveamps.com 
Collector and restorer of old valve guitar amplifiers describes his collection.
http://www.valveamps.comAcme Sound Bass Speaker Cabinets
Andy Lewis' flat-response extended-range "Low B" line of 3-way bass speakers. Direct sales.
http://www.acmebass.com/
Harmony Central Amp Database
Large database of guitar and bass amplifier and speaker user reviews.
http://www.harmony-central.com/Guitar/Data/
ESP Projects
Audio projects including amps and preamps suitable for musical instruments amps, effects, and some neat subwoofer/processor plans for bassists.
http://www.sound.au.com/projects.htm
Compact Bass Guitar Speaker Bottom
Len Moskowitz' famous compact bass cab plans. Gonzo sound for the do-it-yourselfer.
http://www.core-sound.com/bottom-article.html
Bass Gear Review Page
Huge archive of bass-related user reviews including preamps, power amps, amp heads, speaker cabinets, combo amps, and effects.
http://www.bgra.net
Fuchs Audio Technology
Design and hand-build tube amplifiers; includes model speficications and dealer network. Also offer a custom-build service.
http://www.fuchsaudiotechnology.com/
Dana Music
Site from luthier Dana Sutcliffe offers a guide to match Ampeg amps and speakers correctly, as well as downloadable Ampeg manuals.
http://danamusic.com
