There is a sticky at the top of the amps and cabs forum page (from which you posted) with tons of info in it.
Mike @ KCA is your man
I use Doug's Tubes
Eurotubes for JJ's
All mentioned are good sources. If you want NOS tubes in particular, Hi Test Guitars is a very good source. He has all NOS (no ANOS) tubes that come in their original boxes. The only thing I don't like is that he has no medern technology as far as how to pay. You decide what you want or call and ask his opinion, he then tells you the price + shipping and you mail a check or money order.
Go down to the Thrifty Drug store and go to the tube testor. OOOPS wrong century!
No need to. The TV repairman that comes to the house will have a truck full of tubes; at least they used to.