TrueCaller is a global number search with integrated call blocking functionality. TrueCaller has been available over on iOS and Android platforms and it will soon be available over at the Windows Phone Marketplace.
With TrueCaller you can see who is calling by connecting with yellow and white page directories from all over the world. TrueCaller also offers Social Caller ID that lets you know what your friends are up to before you answer their calls by displaying information from their Facebook and LinkedIn pages.
One of the more interesting features of TrueCaller is the ability to automatically block calls by adding unwanted numbers to a spam list. It also appears that you have the ability to tap into a centralized spam list. A list that is created from other users on numbers that have been deemed as unwanted or spam.
TrueCaller is expected to be a free app that should be in the Marketplace any day now. Until then you can check out all the details on TrueCaller from their website.