Dopplr recently launched a new version called "Copenhagen" and amongst the new features there is this possibility to insert new trip to Dopplr directly via Twitter (and also by SMS or email). All you need to do is reply to Dopplr with the trip information (eg. "A trip to Helsinki on May 19 to May 23...

I attended last week Lift08. Great event. All speeches are online thanks to a partnership with TSR/nouvo.ch so you can catch up with the conference (but hey guys @ TSR, where are the permalinks for the video???), but the "networking/meeting people" part and the workshops would remain missing....