According to Hitwise
www.hitwise.com
here's the Top 10 websites based on visits:
1. MapQuest
www.mapquest.com
2. Yahoo! Maps maps.yahoo.com
3. Expedia
www.expedia.com
4. Southwest Airlines
www.southwest.com
5. Travelocity
www.travelocity.com
6. Orbitz
www.orbitz.com
7. Cheap Tickets
www.cheaptickets.com
8. Google Maps maps.google.com
9. Priceline.com
www.priceline.com
10. Yahoo! Travel travel.yahoo.com
I think we are a little farther down on that list :)