A number of people have asked if it is possible to launch RB from the command line. While it is in fact possible, it is an unsupported feature in SQL Server 2005. That said, here's how to do it. You just need to specify what report server to connect to, like this:
Other supported URL parameters are also recognized when passed on the command line, like this:
ReportBuilder.exe /s=http://localhost/reportserver "/My Favorite Report"
ReportBuilder.exe /s=http://localhost/reportserver "/model=/Models/Adventure Works"
Again, this feature is not supported in this release. If you run into problems and call MS product support, they will tell you to go jump in a lake. :)