It is a pretty interesting little application that allows you to import your contacts from your major networks using Plaxo it looks like.
I like how they describe how Pownce is made, check it out.
They have an API as well that lets you access the user information, friends, and notes for the account.
Still wrapping my head around how this fits into your daily activity, but I am sure it will come to me. Looks like it is another piece of the puzzle in helping me get control of my social graph and further complete my single social interface.
Will share information about it as it comes out.