There are loads of such affiliates. Do a google search for whatever travel product you want and then add "affiliate" to the search.
Pingo has a nice international travel phone card that could be a nice up-sell to your travel site. Also I like the poland guide. We have a nice offer on call Poland calling cards at PingoPoland.com
MarketLeverage has some rocking travel deals, I know rocketprofit, azoogle, NBA and maxbounty don't do that badly on that vertical either.
Aditionally, you can a product which helps prevent sunburn, prolong suntan, give the skin a healthy skin, boost energy levels and relieve eating sensitivities. This product is an aloe vera herbal supplemnt called Aloeride and you can easily promote it on your travel site in articles with health tips for travelers. To learn more, follow the 1st link in my signature. Good luck!
Do you see a lot of business related traffic? If so, click on my sig and sign up for a high commission offer that any site would want to be associated with
I'm working with TripAdvisor for 2 years. But since last month, they are not accepting new affiliates. By the way.. Is anyone working with tripadvisor for more than one website like I do?.. I've built up my 3. travel website and I wonder if I could locate same affiliate code that I've been used before.. I've sent e-mail to them but not answered yet. There must be a problem.