Klaus Boening's Analog Audio Web Site
Describes a few tube amplifier projects including schematics and descriptions of the circuitry.
http://www.klaus-boening.de/

Pass Do-It-Yourself
Projects by Nelson Pass including amplifiers, preamps and loudspeakers. Site offers information on circuit boards, FAQs and how to articles.
http://www.passdiy.com/

Promitheus DIY Audio site
Includes projects and articles about amplifiers, preamplifiers, speakers and cables.
http://mitglied.lycos.de/Promitheus/

Wade's Audio And Tube Page
Discussion of vacuum tube audio amplifiers and high fidelity equipment with photos and schematic diagrams.
http://www.angelfire.com/vt/audio/

Gary's Vacuum Tube Page
Vacuum tubes for antique radios and tube audio gear.
http://www.the-planet.org/

Boozhound Laboratories
DIY site specializing in tube audio, vintage style guitar amps, mad science and all around DIY hooliganism.
http://boozhoundlabs.com/

Guitar Electronics Projects
DIY guitar site that features guitar tube amps, pedal building and related projects.
http://www.freewebs.com/amp_build/

nMine.com Developments: Multi-amplification DIY Project.
Description and photos of multi-amp PCB with three integrated amplifiers each PCB and 24 dB/Octave Linkwitz-Riley Electronic filters. Configurable as a bi-amp or tri-amp.
http://www.nmine.com/multiamp.htm

XO - An Excel Crossover Design Tool
Passive 2-way crossover spreadsheet design tool. Models allow complex speaker impedance, acoustic target shapes, series or parallel designs, and impedance compensation circuits.
http://www.geocities.com/mghjch02/

Leon's Audio Page
Showcases the author's build of tube amplifiers, pre-amplifiers and restorations of tube radios.
http://www.leonaudio.gr/

Chris VenHaus Homepage
DIY resource for Audiophiles. Includes recipes for Cat5 speaker cable, fine silver interconnects, and power cords.
http://www.venhaus1.com/

Decibel Dungeon
Beginners guide offers an introduction to DIY hi-fi. Includes articles on building, modifying and buying components.
http://myweb.tiscali.co.uk/nuukspot/decdun/

DIY Audio Projects
A wide collection of DIY Audio Projects that range from chip amplifiers to speakers to tube pre-amplifiers.
http://diyaudioprojects.com

Forum - DIY Hi-Fi
A web community (message forum) for the discussion of DIY Audio.
http://diyhifi.org

Fun With Tubes
Information related to vacuum tube circuits and techniques.
http://www.angelfire.com/electronic/funwithtubes/index.html

Elliott Sound Products
Information for audio DIY hobbyists. Articles, construction projects, links, sources.
http://www.sound.au.com/

Photo Gallery - DIY Audio Projects
A photographic gallery of DIY Audio Projects. The projects include are pictures of speakers, amplifiers, cables and more. Share photographs of your DIY Audio creations.
http://diyAudioProjects.com/Gallery/

CoolTune Audio Projects
Marco Rutz shares his experiences and projects in design, acoustics and recording. Personal observations, current and past projects, photo gallery, and high-end systems are showcased.
http://home.datacomm.ch/cooltune/