TravelAPI

1. AgentFactor Travel

2. BART

3. Chicago Transit Authority

4. Cleartrip

5. Destinde

6. dopplr

7. fboweb

8. FlightAware

9. FlightStats

10. FlightView

11. HotelsCombined

12. Hotwire

13. Kayak

14. King County Buses

15. Lonely Planet 

16. Rezgo

17. sletoh.com

18. SmartTravelDeals

19. Superbreak

20. to.uri.st

21. Transport for London

22. TravEnjoy

23. TriMet

24. TripIt

25. Vianet

26. Yahoo Travel