Hi tahitiangirl,
Check out Richard Wise's blog. He is a wonderful gem expert who is the author of Secrets of the Gem Trade, (which I'm going to buy for a b-day gift to myself this year).
(
http://gemwiseblogspotcom.blogspot.com). I hope I got that address right. He actually talks about the top four sites, which include diamondtalk and this forum and rates them. I haven't read the whole thing yet, but I'm going to!
Laura