Guess we're going to have to keep adding to that list. Yes, the official app for TripIt by Concur Technologies is now available. Up till now, we only had the excellent MyTrips 3rd party app which we still recommend you take a look at, as an alternative. But you can't beat free and so it's nice to see the super popular travel planner service now on Windows Phone.
We actually all use TripIt around these parts when our various Smartphone writers are globe trotting to conferences and events. If you haven't tried the TripIt service, it scans your email for travel information (flights, hotels, etc.) and automatically adds them to your upcoming trips. It's eerily awesome how well it works, allowing you to add things to your calendar, share them with others and just keep all your travel itinerary in one, accessible place.