I like the Glasstek stuff. Top quality stuff and they're easy to deal with.
http://glasstek.com/
There are a couple of others that make good stuff but like Dave said there is some junk out there too. Check the scammers section or if you find something else you're considering post here before ordering. I know the 2 that seem to have the worst reputation here are unlimited fiberglass and bruis glassworks. I personally have used the unlimited stuff and never would again and I have seen a lot of complaints on the bruis stuff in the scammer section.