Awww... this is such a toughie to answer - I've not been lampworking long and almost every thread has helped me immensely, particularly the Q's and A's. Everyone is so helpful and answers daft questions quickly and without any superiority (unlike some other sites).
One thread only a couple of days ago gave me my latest AHA moment -
http://www.lampworketc.com/forums/sh...54#post5035954
Also, but not exactly a thread, the Garage Sale section enabled me to drop on a real bargain when I upgraded from my Hothead last year - a complete set-up with kiln, torch, oxy-con, masses of glass and tools for pretty much the cost of a new torch. It was fairly local to me in the UK too, so this site is invaluable no matter where you live.