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