Sites I have personally bought from:
(Recommended)
http://finertimes.com/index.html
http://www.girards.com/
Sites that I have corresponded with but not purchased:
(Seem legit and I would purchase from)
http://www.secondtimearoundwatchco.com/
Sites that I have not purchased from but have heard good things:
(Caution, do your own research)
http://www.bernardwatch.com/
http://watchestobuy.com/
http://www.watchcat.com/index1.htm
I know of many other sites that I know nothing about or have heard a few bad things, so I will not list them on this page. Do copious amounts of your own research before buying from any online Vintage Watch seller. Remember, you do not have the watch in hand, so assessing the condition of a watch through pictures online is risky at best. Sites that I have bought from have been straightforward, quick to respond, and pictures and descriptions were accurate. The watch I received was in the condition and item that I thought it would be based on my online observations and emails to the sellers. Especially with vintage items, most sellers are reticent to take returns so the Buyer Beware!