Dopplr has been in private beta for a while, and it appears to be starting to stretch its wings and take on more testers. To this end I've now got "unlimited invitations" to give away. However, to maintain my sanity - and the ethos of Dopplr - I'm restricting the invitations I give away to friends, and people I "know" online. I'm not being overly picky, but if I've never heard of you, sorry no invite.
For some background, Dopplr is aimed at increasing serendipity for frequent travellers. Dopplr's CTO Matt Biddulph has written a good overview of Dopplr's intent. For further background the Dopplr blog is worth reading too.
My two-pennorth on Dopplr? I like it so far, although I don't travel enough to make it truly worthwhile; the attractive interface is minimalist, verging on spartan. The best bit for me is that "it just works", nothing fussy, nothing too prescriptive. As someone who seems to live their life via IM, a Jabber interface would be useful, but the sms, web, and rss interfaces cover all the essentials. There is an api in the pipeline, so perhaps I could write a Jabber bot for this anyway. The Dopplr approach to feature-creep appeals to me, although it does make me a little wary of requesting new bells and whistles.
Still puzzled by Dopplr? their About page sums it up better than I can (snippet below):
Dopplr is an online service for frequent travellers. It was created by an international team of world travellers as a tool for our own use. We liked it so much that we decided to open it up to our global friends.
If you travel more than five times a year and have friends who do as well, then Dopplr is for you.
How does Dopplr work? It 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. You can use the service with your personal computer and mobile phone.