Recently made available on Autodesk Labs, the Solar Radiation Technology Preview for Revit 2011 delivers an integrated and visual analysis experience.
This updated preview takes full advantage of some new functionality in Revit 2011, for example use of the new Analysis Visualization Framework API is shown off here for the first time (The Analysis Visualization Framework is a mechanism for an analysis application to easily display computation results as transient 3D data in the Revit model).
The Solar Radiation Technology Preview for Revit 2011 allows you to understand and quantify solar radiation on various surfaces of your building information model.

Go download from Labs: http://labs.autodesk.com/utilities/ecotect/
and read more on the It’s Alive in the Lab blog ..

There is even a new discussion forum specifically for the Solar Radiation Technology Preview for Revit.