lattest gimp version:
I read a bit of ubuntu forums and found this...
If you really want to defy the ubuntu philosophy you could try downloading the source http://mirror.umoss.org/gimp/gimp/v2.6/Adding repos for packages that aren't compiled against the distro/version that you're running is a bad idea. While it's theorectically possible, the potential for mass system breakage and headaches is too great, IMO. If you aren't running Feisty, you could always upgrade to get the latest packages. Otherwise it would be best to wait for Gutsy to be released.
Ubuntu philosophy is to be very stable. The trade off is having relatively "out-of-date" package versions to accomplish this.