When you receive a call on your Android phone from a user in your contact list, you see a screen that displays the caller's phone number and their name.
If you have a photo assigned to them, you'll see that as well. From there you can accept the call or decline it. Unfortunately, the default caller ID doesn't give you more options or information than that.
Enter PhoneTell, a new Android app that displays much more information about the caller if it's available, including their phone number and the location from which they are calling. The app even allows you to send the caller a short SMS if you decline their call, which lets them know you're busy and will call them back.
You can Free download PhoneTell from the Android Market, or from developer’s page.