Sectional Perspectives! - for later versions as well

1. Go to Ground Floor Plan, place a camera face on to the plane you want to cut
2. When the camera view opens, tick 'section box'
3. Click on the section box boundary to activate the grab handles and open the floor plan view again - section box lines should still be highlighted for you to move (if not, go back to camera view etc)


For later versions of Revit, see this tutorial: http://www.youtube.com/watch?v=oaRcLLXsOq0