Try Accurender's site and there are some tutorials in Revit's HELP menu on presentation and rendering. Also, the complete Revit tutorials and documentation can be found at http://usa.autodesk.com/adsk/servlet/item?siteID=123112&id=9481365 and if you are on subscription there are tutorials at http://pointa.autodesk.com/local/enu/portal/vip/members/resource/lc/elearning.jsp?cf=Revit%20Architecture%20(Autodesk%20Revit%20Building). Plus many sites as AUGI, Revitcity, BIMWorld and the plethora or BLOG sites have other tutorials or tips on rendering in Revit.
Mel Persin, AIA
AEC Technology Consultant
Technology to Visualize and Realize Solutions
Modeling the Future/Drafting the Past