AMD (ATI) Catalyst 11.4 Released Just In Time For Ubuntu 11.04 Natty Narwhal

http://www.webupd8.org/2011/04/amd-ati-catalyst-114-released-just-in.html

~ Web Upd8: Ubuntu / Linux blog

A quick update: AMD has released Catalyst 11.4 with support for X Server 1.10 so all of you who want to upgrade to Ubuntu 11.04 Natty Narwhal should now be able to use Unity.

I do not use an ATI graphics card so I can't really tell you how everything works so all I can do is give you a download link:

Download ATI Catalyst 11.04