This is a good one!
A backlink checker that checks up to 3 url´s at once.
Simply fill in your domain names and press submit.
You will now find out who links to you on Google, Yahoo, All the web, Altavista and MSN.

Try it out here: Backlink checker

A smart thing to do is to bookmark your result so you don´t have to write in the domains again next time you want to check your backlinks stats.

This tool comes from: http://www.searchengineoptimising.com/

If you find other good backlink checkers please post them here.