twitter friends

This will give you a break down of the twitter friends you have in common with all the rest of your friends or between any two screen names. If you enter one twitter screen name you'll get a chart like this (for example); if you enter two screen names you'll see the intersected friends as images like this.

User id 1:

User id 2:

If it's not working it's because it's being rate-limited by twitter...they allow 100 requests per hour.