Here is one of the most surprising and promising recent news items for Revit API developers, published yesterday by Emile Kfouri on BIM Apps: The Revit STL exporter is now open source.
Look at Emile's post for the complete story, including:
To add an unrelated technical note, here is a very quick little question that crops up from time to time:
Question: How can I a parameter to an existing family?
Answer: You can add a real family parameter directly using the FamilyManager AddParameter method taking the arguments string, BuiltInParameterGroup, ParameterType, Boolean.
Alternatively, you can create a shared parameter definition and add it to family using the FamilyManager AddParameter method taking the arguments ExternalDefinition, BuiltInParameterGroup, Boolean: