To be on the safe side, I rely on mysimon.com a lot. If I can't find it there I hop over to google.com and look around. Be very careful though. Remember that ANYONE can start up a website and appear to be a reputible sales group. If you find a site and you feel a bit sketchy about it, come back here and we'll give you our experiences and opinions on how they do business.
There are tons of sites out there, and I remember there being a lonnnng list posted here somewhere (do a search for it). Just take your time and do your research.
