There is an online version of the Revit 2010 help files:

• Revit Architecture 2010
• Revit Structure 2010
• Revit MEP 2010

I tried it in Firefox 3.5.2:
Even though there are a few layout problems, the rest works.

I just wonder why, since when I need the help I am usually using the program anyway and I thus have access to the local help file. No internet needed.