Can I still download free trials of Revit 2012?
No, Autodesk Revit MEP 2012 is not available for downloading. You can download only the latest versions released by Autodesk and that can be done on the link posted below. Of course, there could be other users hosting the download for the Revit 2012, but I wouldn't recommend that since the packages might be infected with malware.
Official download page: http://www.autodesk.com/education/free-software/revit