As part of Autodesk's ongoing commitment to sustainability, they have released a technology preview of a Solar Radiation tool for Revit Architecture and Revit MEP 2010. You will need to make sure that you have web update 1 installed, but the preview can be downloaded from the Autodesk Labs web site.
http://labs.autodesk.com/utilities/ecotect/
This is an exciting development, because for the first time the architect will have graphical analysis tools embedded within the Revit Architecture environment.
