Audio Tube Data from Italy. Comprehensive site with a lot of very useful information.
http://digilander.libero.it/paeng/devices_frame.htm
Vacuum tube sockets for sale.
http://www.tubeworld.com/sockets.html
Some great tube history and data!
http://www.ominous-valve.com/tubes.html
Some pictures of Nixie and other types of old and unusual vacuum glass tubes.
http://pobox.com/~JasonHarper/Nixie.html
Articles about tubes. Primarily geared toward audio applications.
http://soundstage.com/tubeor/tube.htm
Nolan Lee has this file with useful information on the tubes tester and its adapter kit for use for testing miniature tubes.
http://www.acadiacom.net/nlee/i177_index.html
Resource for the TV-2, TV-4, TV-10, and I-177. Military surplus tube testers.
http://www.acadiacom.net/nlee
Audio tube related link list, forums and newsgroups, tube amplifier collection and tweaking. Audio amplifiers that use tubes. Tube replacement list included.
http://www.worldtubeaudio.com/