Referred to as Web Update SP2, find out all the information on the latest English language build for Revit Architecture 2008 here: http://www.autodesk.com/revitarchitecture-download
Also… There is a new build of Revit Structure 2008 -read about it on BIM & BEAM


As of the writing of this post, the most current version of Revit MEP is: Revit MEP 2008 build (2007_0615_1700)
The download link for Revit MEP is: http://www.autodesk.com/revitmep-download
Update: There is now a Revit MEP Web Update #2 build (20070829_2300) as well. The fixes in this update are significant enough that it is well worth the update of your current version.