B & H Photo and Video (
http://www.bhphotovideo.com) remains one of the best online sources for purchasing photo and video equipment.
They will usually give you a good lead time on any items not in stock, and the manufacturers like to take care of them since they move so much stock.
I received my new B & H Camera Catalog today, which is worth it's weight in tips, not to mention product...and it's free.
ADG Webmaster