Blekko is a new search engine that allows you to use "slash tags" to order and filter results. For instance you might search for "Iphone /reviews" to just see reviews of the iphone or do a search for "blogs /humour /politics"
Checkout these video for more info http://blekko.com/ws/+/press-videos?h=1
The Blekko team have already created and tagged thousand of websites but the idea going forward is that users will create and share their own tags.
Checkout these video for more info http://blekko.com/ws/+/press-videos?h=1