Bing Travel is a free travel planner for Windows Phone. The application combines destination recommendations with flight and hotel searches. You can even book your trip with the app!
Bing Travel packages trip ideas, travel news and destination guides in a neat interface. You can search for and book flights from multiple airlines, look for hotels and reserve rooms (viewing Tripadvisor reviews), and check flight statuses.
It's a bit light on content but Bing Travel is a fast way to plan a trip.