I have bought everything I have from B&H Photo in NY and also Camera World in Oregon. No problems with them and that includes the purchase of a used lens that was $3,600. Trust me that was scary.
I can back-up B&H as well, they run a reputable business. Another I have had good luck with is KEH.com. I've purchased used equipment from them in the past and it is very reasonable and always in good shape.