Have a look into http://flashgamelicense.com if you haven't already. If you have a quality game, you can actually end up with a bit of a bidding war going on between potential licensees, and most deals allow you to sell again to other sites after an exclusivity period. Each of our Pretender games so far (http://launchingpadgames.com/games/the-pretender-trilogy/) has earned in the high four-figures, with zero in-game advertising except for fairly tasteful co-branding from the sponsoring sites.