I have used Pete Rizzo, Chuck Smorse and Andy Hughes.

Pete Rizzo operates a website called www.oldvegaschips.com where you can find new releases at great prices as well as a ton of information about chipping and scans of old Las Vegas chips that you won't see anywhere else. Pete and Chantal give great service and I highly recommend them.

Chuck Smorse offers great service and extremely reasonable prices by allowing you to pre-order your chips before they are released. If you get on Chuck's mailing list he'll send you an announcement of an upcoming chip release, with a scan of the chip. You just let him know if you want it. Here's a link to more information and his e-mail address: http://www.thechipstop.com/chuck.html

Andy Hughes has a great selection and also offers excellent service at his website:
http://www.nevadacasinochips.com/

You can't go wrong with any of these guys!