I had to do this the other day and here are the short and curlies of doing it.
If you have SQL 2008 installed the RSWebParts.cab file can be found @
C:Program FilesMicrosoft SQL Server100ToolsReporting ServicesSharePoint
The stsadm.exe can be found here on a 2010 SharePoint install
C:Program FilesCommon FilesMicrosoft SharedWeb Server Extensions14BIN
Cd to this directory and run this command
STSADM.EXE -o addwppack -filename “C:Program FilesMicrosoft SQL Server100ToolsReporting ServicesSharePointRSWebParts.cab” -globalinstall
The webparts are now available in SharePoint.
They show up under miscellaneous, when you try to add a web part