Although some packages for Raring are starting to arrive in the AMD Catalyst Legacy ppa
This ppa works for Precise and Quantal, I'm using it for Quantal myself.
This repository is downgradeing X-Server from 1.13 to 1.12.4 (which is maximum version supported by the drivers). Also driver Catalyst 13.1 (fglrx 220.127.116.11) is patched with this:
(comment 14), so it could work on Linux kernel 3.5.