What's a good alternative to Dopplr?

I have never used Dopplr but from what I see it seems very similar to TripIt, which is a popular option for itinerary tracking/planning. Depending on what place you're visiting, Lonely Planet has a selection of mobile apps for recommendations and places to see. I also use Foursquare to keep a log of places I have visited, and it can sometimes be good for recommendations too.

I used dopplr for a while before switching to tripit. It is basically the same service. Add your travels and your friends can see where you are. The dopplr site looks nicer but lacks the outstanding mail importer of tripit. Just forward a flight booking andit gets into your new or existing travel. Tripit was also first with linkedin integration. I don't know if dopplr is there yet. Probably not given their new owner structure....

I don't know Dopplr either, but based on your description I would say Google places and Google Latitude is doing some of what you want.

I wrote InTractu service to keep not only places, but also ways I've been traveling. It remembers the ways and is able to visualize them all on the map.

For now it works only on mobile devices, but sometime soon I will release www version, showing traces of flights, visited cities and some other data that can be extracted from GPS data the phone is gathering.