When you sign up for Dopplr you can find out who else you know is traveling to the same place you're going at the same time. Then maybe you can meet up for lunch and you won't be alone through the whole trip.

Enter all your upcoming travel plans into Dopplr. Enter all the places you're going to be while on your trip. When your friends, co-workers and acquaintances enter their plans you'll both be able to see when you'll be in the same place, at the same time. Then you can make plans to get together and meet up for something fun.