The following are some of the best site’s I’ve found that deal with the Revit API, as well as other issues revolving around automation and interoperability through other programs.
The Proving Ground , Nathan Miller
Excellent blog that deals with many instances of Interoperability. Specific code examples for Revit API .CSV XYZ import and Mathematical surface generation available.
The Building Coder, Jeremy Tammik
A very thorough blog that deals specifically with using the Revit API to automate tasks in Revit. Many example scripts available. Whilst not dealing directly with Interoperability issues, this is the best place on the web for Revit API assistance.
BIMBOOMBAM, Michelle Van Kolck
BIM focused blog, somewhat Revit-centric that explores the possibility of BIM data being shared across different CAD platforms.
GeometryGym, Jon Mirtschin
Geometry Gym is a blog almost solely dedicated to solving interoperability problems. For a link between Grasshopper and Revit Jon is utilizing the IFC (Industry Foundation Classes, an object-based file format with a data model developed specifically for use in the building industry for interoperability purposes) as the means of translation. The IFC Wiki also has some great links to example interoperability projects (see below).
Buildz, Zach Kron / Joe Kendsersky
“Practical notes on making impractical things”. Whilst not delving into the scripted side of interoperability Joe offers many useful techniques for transferring 3D models between various software.
Revit VB code examples and a good discussion thread of the possibilities/ techniques available when using the Revit API.
DesignReform, CASE Inc.
Design reforms provides many resources to the building technology minded. Excellent video tutorials in addition to a strong user community
AutoCAD, Revit Documentation
VB Code examples and in depth documentation on the Revit Platform.
White paper dealing with Interoperability issues relating specifically to a link between AutoCAD and Revit. Methodology revolves around exporting 2D Revit drawings onto empty AutoCAD sheets and then linking the files via the “Import/Link” command.