A travel search engine can be found at
BestTravelCoupon.com. It's a free site that allows you to enter your destination and dates and the "search engine" will find the lowest possible rate for you.
The site at
Travel-Search-Engines.com, is a review site for different travel booking sites. In 2013 the rated BestTravelCoupon.com and Kayak.com as the best search engines for travel deals. However, I have noticed Kayak.com tends to fall short on hotel rates. On this site you can see the 2013 rate comparisons between BestTravelCoupon.com and Kayak.com. In 90 different rate comparisons, Kayak.com had the lowest rate on only 5 out of 90. That's roughly 6% of all searches. Not a good showing for Kayak.com.
The problem with Kayak.com is it tends to post results from only Expedia and Priceline, while BestTravelCoupon.com searches more travel sites, provides more travel options, and consistently delivers lower rates.
In this document you can see the complete results of the 2013 rate comparison with Kayak and BestTravelCoupon.