... more importantly, where not to. One photographer's opinion.
My experience is much more limited than Steve's. However, I agree with his ratings of B&H Photo, Amazon, and Ken Hansen (Ken just sold me my second Leica). I too had a little bit of difficulty buying from Pop Flash Photo through eBay. And YES, stay away from Brooklyn Camera stores. Their distasteful tactics are legendary. I do not understand why photo magazines accept their ads.