New FREE Keywords Tool for Mac OSX Leopard - still in Beta
They say - "The top domain view in SEO Lab allows you to quickly see the domains of sites that are ranked on the top for any keyword phrase.
The domain names are extracted and displayed along with the strength.
The site strength is calculated on the basis of the ranks in search engine results pages (SERPS). The top rank of the domain at the three search engines are also displayed.
You can identify the top sites that are in direct competition with you."