In SSRS 2000, there was a specific location on the filesystem where you could drop RDL documents so that they'd show up as possbile new report choices when a developer chose to create new report. The same holds true for SSRS 2005:
C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\PrivateAssemblies\ProjectItems\ReportProject
If you browse to this location, you'll notice (among other things) a report.rdl document. This file represents the "Report" item you see in the SRRS Project Items dialog that you choose from when you create a new report. You can do two things with the folder above: