I found this PPA which features MySQL 5.5 (alongside php 5.3.8 packages..):
https://launchpad.net/~nathan-renniewaldock/+archive/ppa
Seems to be working fine on my 11.10 Ubuntu, ut I can't find anything on the person/group behind the release.
Is this PPA trustworthy? Do you know anything about "Nathan Rennie-Waldock"? Is there any other alternative?