TripHub has been flying under the radar for a number of months. But the Seattle online travel startup -- founded by former Expedia manager Josh Herst and backed by Madrona Venture Group --is officially taking flight this week.

TripHub's free online service is designed so that friends, family and classmates can jointly organize group vacations. The service allows travelers to invite guests, research hotel options, add photos, share itineraries and track who owes money.

The company's board of advisors includes Zillow.com Chief Executive Rich Barton, Farecast Vice President of Marketing Mike Fridgen and RealNetworks Vice President Dave Richards.

It is kind of interesting how Seattle has shaped the online travel industry. A lot of people forget that Expedia was born here -- spun out of Microsoft in 1999 and now operating as a separate company in Bellevue.

But in addition to Expedia, a number of online travel startups got started in Seattle. Maybe it is the rainy weather.

Off the top of my head, I can think of Escapia, RedWeek, Farecast and VacationSpot.com (purchased by Expedia in 2000). Let me know if I am missing any (I had heard that some former Microsoft guys had started an online travel company that searches multiple providers, similar to Kayak.com. But I don't know the name).

UPDATE: Just heard back from Josh Herst, who founded TripHub last year after spending some time at Madrona. The idea, he said, came after thinking about his own group travel experiences and talking to others about the challenges of putting together vacations with multiple participants. He declined to say how much the company has raised.

So far, Herst said the reaction has been positive with church groups using the site to put together retreats, young men using it for bachelor parties and families to organize ski trips. TripHub plans to make money by selling hotel rooms, referrals to other travel sites and advertising. It also is running a co-branded group travel site on behalf of Alaska Airlines.

Herst said online travel sites such as Expedia and Orbitz are "optimized for individual travelers" and don't have the tools to organize group trips.

Speaking of travel, Travel + Leisure magazine just named the 35 innovators who are "making travel safer, sexier and more streamlined. A couple folks from Boeing and the co-founder of clothing company ExOfficio made the list.