The final version of the Feature Builder Power Tool designed to work seamlessly with Visual Studio 2010 has been released to the gallery.
Download it from here. There are a number of videos up on channel9 that you can check out to understand what Feature Builder is exactly by clicking on this link.
A real world example of how an internal Microsoft team has taken advantage of Feature Builder can be seen in this video. It is basically a video talking about how the Feature Builder was used in the latest Hands On Lab for Windows Workflow 4.