There are a growing number of companies creating specific products intended to expand or enhance working with Revit.
Building Framing and other Utilities:
Recently Tools4Revit made their work available to me and I've been slowly working through their pretty comprehensive set of tools. I plan to post about some of their tools as soon as I feel competent to do so.
Site and Land Development:
I hope to get a chance to see the latest development from Eagle Point Software called LANDCADD for Revit. LANDCADD is hardly new but support for Revit is brand new, new enough that there isn't much information on their site yet. The release is tentatively scheduled for October 2009. You can read their press release HERE.