I really, really like the look of this application from TrueCaller.com. All you need is a 3G or WiFI connection and when a number rings you that:

a) Isn’t already in your phone
b) Isn’t anonymous

Soylent Green release It goes and looks up the contact tells you who they are!

The Ballad of Josie full

It doesn’t appear to work in the UK at the moment – which is a REAL shame!