Open Source Software to open PSD files

I am working for a webdesign company, creating Joomla templates. The problem we had is that they do all their web design in Photoshop and then export it as .psd (Photoshop Document) files. Unfortunately I don't have Photoshop and it didn't really seem worth it to buy Adobe's (expensive) product just to edit PSD files. So I tried looking for open source (or freeware) alternatives.

The best option I found was GIMP (GNU Image Manipulation Program):
http://www.gimp.org/

which is not only a nice .psd editor but also a good image manipulation program available under the GPL (GNU General Public Licence).