trip intersection service Dopplr out of beta, open for signups

Dopplr is a site where you enter your planned trips, with dates and locations, and then share those trips with (selected) others in the Dopplr social network.  The site will then inform you when you have trips that overlap with your contacts.  It's good e.g. if you tend to circulate around conferences, and would like to know who else is going to be in the same city when you are (or who lives in a city you're going to visit).

They just opened out of beta to the public at LeWeb3, on December 11, 2007:

Enabling coincidence, and spreading quickly

Dopplr lets you share your future travel plans with a group of trusted fellow travellers whom you have chosen. It also reminds you of friends and colleagues who live in the cities you’re planning to visit. For example, Dopplr might tell you that three of your trusted friends and colleagues will be in Amsterdam when you are planning to be there.

In recent months Dopplr has become an essential tool for users around the globe. Many joined the service after invitations from friends and colleagues.

Dopplr launches at LeWeb3 in Paris

I've found it useful, of course the more travel you do and the more people you're willing to share with, the more you will get out of it.