diytube.com

Located near the home of Mickey Mouse, in Orland Florida:

http://www.vacuumtubesinc.com/index.html

I've heard good things about them, and they have some reasonably decent prices.

Also an interesting section on faked / mis-marked tubes to be wary of :o

/ed B in NH

Ed,
I've been ordering from that spot for about a year. For sockets and not-so-commonplace tubes you can't beat 'em.