Autodesk Labs provides free technology they are currently testing, not to be mistaken for beta testing. They are relevant tools to the industry, and they look for feedback from clients to verify whether or not the tools would be good for to put out or add to existing software products, like Revit. Project Vasari and Photofly both are on the site, and functionality from Project Vasari have been added to the Revit platform because of feedback and excitement.
Autodesk Seek was created to share Manufacturer specific content created in Revit to the AEC community. Free to the AEC community, many clients have benefit from using the Revit Families up on this site. Each Revit platform has a direct link to Autodesk Seek. There are guidelines and technical requirements for Manufacturers.
Green Building Studio
Green Building Studio is a web-based program that comes free for clients on subscription using any of the Revit platforms or Ecotect (there may be others, but those are the ones I am familiar with).
More information on: http://usa.autodesk.com/adsk/servlet/pc/index?id=11179508&siteID=123112
This program is a whole building analysis software that assists in qualification for LEED 8.1 Daylighting credit, water usage and cost, Energy Star scoring, natural ventilation potential, carbon emission reporting and more.
All three Revit platforms have extensions available. I find those for Revit Structure to have the most extensions that will provide an immense amount of efficiency for the client. The Reinforcement Extension alone will help any client looking to model the rebar in more than one element at a time. The Wood Framing extension (also beneficial for Revit Architecture), Freeze View extension, and many more are fantastic!