Lots of people do, although it really seems like the diehards stick to the official site for forum activities.

I have no active campaigns, but I've played LBB (w/ and w/o the added supplements), Megatraveller, GURPS Traveller, T20, Mongoose v1, and tried T5.0.

GURPS Traveller is a pretty good fit--GURPS Sci Fi and Space conventions were already established as Traveller-esque (the various weapons and armor match up with Traveller equivalents, etc.). Which makes sense, since there was a lot of fan and writer overlap in the early/mid-80s. The big thing I dislike about the GURPS version is that it misses out on the character creation career rolling, which, although it violates some peoples' opinion on inter-PC balance, is a heck of a lot of fun.