With my recent source control issues it appears I lost several RDL's, I came across the Reporting Services Scripter which allowed me to extract all the RDL files from my reporting server - very sexy.
Nice - although when something similar happened to me I just navigated to the reports area and downloaded the RDL files I wanted from there
The tool is useful if you have a lot, and need them all though!
This page shows you how to get the rdl definition from the SQL table
mscrmuk.blogspot.com/.../reading-rdl-definitions-directly-from.html