Tekla BIMsight is a feature-rich tool for online project collaboration. It can be downloaded free from Tekla and freely distributed, what makes it a practical and affordable solution for projects in which players of various calibre take part. I only had a brief trial of the tool. But the details on their site show rich features like IFC support, 3D Navigation, Measuring, and Automatic Clash Detection. Further, they provide an API for direct exporting of Revit projects to Tekla.
View their introductory video below.
Tekla introduces BIMsight with the premise "Fragmented and inaccurate project information leads to delivery problems in the building and construction industry. Securing information flow and accuracy results in less costs, less waste, and projects delivered on time". I feel that they have achieved a lot and hope they'll continue to further develop.
They provide good tutorials for you to learn Tekla BIMsight.