What's a good website to describe different tubes?

You can try searching the tube and SET forums @ audioasylum.com. Not a lot of shills there (though I am aware of one tube dealer who posts as a private member) and it's pretty good info to sort through.

You are better off looking @ tube rec's for your particular gear if you are purchasing tubes for such as more important than a tube's sound is the circuit that it is used in (bad circuit design or a bad tube match to a circuit equals bad sound).

I remember that Viridian researched available info on the net. Why not ask him

thetubestore.com Compares the sonic characteristics of tubes in guitar amplifiers

upscale audio site has some good information about tubes.