ROBOT Millenium Freeware is a Windows-only structural engineering program, with a direct link to Revit Structure, 2D and 3D Frames (limited to 200 members) and plates and shells (up to 1500 nodes). Registration is required. Edit: it seems that the page is unavailable at the moment. Would the acquisition by Autodesk have something to do with it?
Info on BIM, CAD & 3D software for architects and students