In addition to running scripts designed for the GIMP you are also able to run many 3rd party Photosop Plugins within the GIMP thanks to PSPI. Originally written for the Windows version of the GIMP it has also been ported to Linux.
I have been using the standalone version of the PTLens application for a couple of years for fixing distortion within images. I gave the Plugin version of it a try using PSPI. It seems to work well without any problems.
I also tried some of the Flaming Pear plugins which seemed to work fine too. Many software vendors offer trial versions of their plugins. Just do a google search and you should be able to find plenty to choose from.