I've just released an update to the free caller ID app I thought might be interesting to people.
http://market.android.com/details?id=com.jagoe.socialphone
In addition to region and carrier info, the new version allows you to tag calls/contacts and to see the tags that other people have left.
Caller ID information can be reviewed in a call log and you can view a tag cloud that shows popular tags for people in your address book or for people who have called you.
Would love feedback if anyone has ideas on how to improve the app.