New SharePoint 2010 Content Query WebPart (CQWP)
The SharePoint 2010 Content Query WebPart have this new feature the Content to Content concept.
Content to Content introduces two tokens that can be used in the Content Query Web Part filters:
This makes it extremely easy to provide functionality such as related content.
Another interesting new feature is the possibility to add new Fields To Display just by adding the to the XSL used in the CQWP, see this post on Liam Cleary blog.