www.autodesk.de has an extended post on how to view Revit files for free at this link:
Autodesk – Autodesk Revit Viewer Free

The page reviews the following methods (none of which are very exciting):

For Revit files There are various possibilities.

Display native Revit files
  • Revit installation in viewing mode
Viewing exported data
  • Viewing DWF in Autodesk Design Review
  • DWF viewing in Internet Explorer
  • DWF Viewing into NavisWorks
  • Viewing in NWD NavisWorks Freedom

The English equivalent to the .de page is considerably shorter:
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=7290003&linkID=9243099

Ok, the review quoted below may be biased, but the Solibri product is worth keeping in mind.  They also make a free IFC Optimizer that can be useful when moving a model from ArchiCAD into Revit.

Navisworks is now an Autodesk product, with a vast sales and marketing machinery to boost its implementation, so this is understandable. But Solibri Model Checker does so much more than Navisworks, and while it has its share of success stories, especially in Europe where Solibri is based, it does not enjoy the perception of near-ubiquitous adoption that an application like Navisworks has, at least in the US. Solibri Model Checker is gaining some momentum in FIATECH and the GSA, which is promising.

via
Solibri Model Checker v7: AECbytes Product Review

Image from AECbytes review page