Well, I've spent enough time on this board talking about the companies that ticked me off, now I should mention the ones that I like (the online ones anyway, since that is what the thread is about).
Central Parts (the link is already supplied in Slim Jim's reply)- this company is at the TOP of my "gotta love 'em list. The site is easy and professional, email is responded to quickly, and you can question them to death and they don't mind a bit. They are truly concerned with getting you the right part. Do yourself a favor and get their catalog- it's very nice and full sized (unlike those "pocket versions" from others.