What release of Inventor are you using?
In Inventor, you can save the Inventor part or assembly as a DWG solid model. Revit will open that model. However, there is no parameter transfer, no iPart transfer, just a basic solid model.
In 2012, use Application menu > Save Copy As > DWG
In 2011, Environments tab > AEC Exchange > Save As DWG Solids
IMPORTANT: Inventor has a different UP axis (Y) than Revit (Z) so Inventor models may arrive in Revit lying on their side. You would need to reorient them in Revit or in Inventor prior to saving as a DWG solid model.
Bill Bogan
Autodesk, DLS, LX Team
Apologies, minor correction....
It's not Save Copy As... It is Export > Export to DWG that you should use for 2012.
Bill Bogan
Autodesk, DLS, LX Team