With so many online travel sites crowding the market, you’d think we were nearing a Web 2.0 travel bubble. But according to travel information search engine UpTake, which is launching May 14, there’s still an untapped niche in the market: a travel-opinions supersite.

The market is extremely fragmented with thousands of micro-sites for individual hotels, beaches, airlines and leisure activities. UpTake’s goal is to gather opinions from all of those sites together and become the most comprehensive research tool used by travelers.

“The booking sites are good when you know that you’re going to Maui on May 17 and want to stay in a Hilton Hotel. But if you don’t even know whether to go to Maui or Kauai, it’s not that easy,” said CEO Yen Lee, who was General Manager of Yahoo Travel before he left to start UpTake in late 2006.

The site features a personalized filter that, unlike traditional search engines, lets you customize your search according to profiles such as “kid friendly”, “beach”, “romantic” or “adventurous”. These keywords are matched againt a database of more than 20 million traveler opinions from more than 1,000 review sites across the web, including WAYN, TripSay, IgoUgo and, potentially, another newcomer by the name of Tripwolf (more on them later). The ratings collection now spans about half a million places to go, things to do and places to stay. The database will expand rapidly, according to Lee. Searches will be matched with search word ads displayed along with non-commercial search results.

A traveler with unclear travel plans visits, on average, 22 sites before booking a flight or hotel, according to a recent study by Google and Comscore. UpTake wants to turn these 22 jumps into one smooth stop. “We’re like Google, but we’ll only do travel”, said Lee. But he added that unlike Google , UpTake’s database is prepared to ask travellers the big questions: why they’re travelling and who they’re travelling with.

UpTake is most closely related to travel research site TripAdvisor, which according to Comscore has a 5 percent global share of the travel research market.

UpTake doesn’t have the booking elements of sites like Expedia or Travelocity, or the price-comparison features of Forecast, TravelZoo or Kayak. It doesn’t have any of the post-traveling services of travel communities like RealTravel, WAYN, Tripsay, Dopplr or IgoUgo either. These areas of the online traveling market are already well enough served, according to Lee.

The number of social travel communities is steadily climbing, though. Tripwolf, which I mentioned above, is yet another travel community planning to launch soon. Scheduled to begin service in June, it will have recommendations features similar to WAYN and TripSay. It will also let you look at pictures and listen to sounds from different destinations to get a more genuine feel. Its biggest plus is the recommendations by locals who know the locations better than any temporary visitor.

Travel is the biggest e-commerce category with $96 billion spent globally on business and leisure travels booked online in 2007, according to Comscore. The travel lead-generation market currently comprises about $1.5 billion, according to Lee.

There’s certainly a market for comprehensive travel research services. Everyone realizes this, including Google and Yahoo, which are likely to continue improving their own travel search tools. But building up a viable user base won’t be easy for a newcomer like UpTake. And the toughest challenge remains offline. A good chat with friends is still a very good alternative to visiting 22 sites before going to Hawaii.

UpTake is headquartered in Palo Alto with engineering teams in Beijing and Moscow and currently has 20 employees. It recently changed names from Kango to UpTake after a name dispute with a company called Kaango.

The company raised $4 million from Shasta Ventures last fall. No new funding rounds are scheduled, but Lee thinks the lead ads will return a steady revenue stream as soon the sight is up and running.

His outlook on ad revenues does seem unusual for travel sites, and maybe a little optimistic, though. “To this end, we help consumers find non-commercial products like beaches, parks and campgrounds that are critical to great vacations but that we can’t sell ads on. But we assume that 50 percent of the traffic on the site will have the potential to generate revenue”, he said. That, despite the fact that the market trend indicates a falling number of paid clicks amid a growing number of search queries, according to Comscore. Very few sites reach a paid click rate higher than 20 percent.

Also, in the currently weak economy where consumers are spending less, it is reasonable to assume they will be clicking less on vacation ads. A weak economy also means that travel advertisers afford to pay less for search word ads at sites like UpTake.

VentureBeat will get back with more details on UpTake that are not being released until the launch.