I’ll start it off and maybe a MOD can make it sticky?

http://www.ofrei.com/WatchBandsAndStraps.html

http://www.sirtoli.com/

http://www.timecafe.com/watch_straps.htm

http://www.watch-bands-straps-bracelets.com/shop-watchstrap.html

http://www.fredawatchstraps.com/

http://www.watchband.biz/

http://www.watchnetwork.com/watchstraps/index.html

http://www.coolwatchstraps.com/…

List of Online Watchband Retailers