Vertical searching is hot these days, and several sites opened their doors offering this kind of service. In the travel business, Kinkaa offers this service to it's visitors.
Based in Germany, Kinkaa finds the best deals for travelers by searching at one click over 100 international online travel websites and portals. The site navigates easy, AJAX makes it smooth and softtone colors were used in the design making it very comfortable to look at. If you've ever planned a trip that was more complicated than going from a to b, you know what a terrible job it is finding matching flights, comparing prices and whatsoever. Those days are over.
In my search I did when trying out the service, it showed what resources it checks when looking for flights :

Results include 10 merchants - aa.com, continental.com, cheaptickets.com, 1800CheapSeats, Onetravel, swiss.com, ba.com, united.com, travelocity.com.

Kinkaa is currently the only independent vertical search provider in Germany.

Kinkaa was founded in 2006 by Torsten Jacobi, headquartered in Hamburg, Germany. Kinkaa made it's debut at ETRE (http://www.etre06.com), the European Technology Roundtable, in Barcelona (Oct. 8-11).