I would like to share a tool I have developped when working on Plee the Bear and Andy's Super Great Park. This is a sprite packing software that works on Gimp images and produces PNG sprite sheets.
The software is Pack My Sprites. It is written in C++ and relies upon Gimp and Xcfinfo to build the sprite sheets. The source code is available under the terms of the GNU GPL version 3. Only the source code is available now, there is no binaries yet.
Right now it is mostly for Linux users since Xcftools is not available for Windows yet. As soon as I manage to build Xcftools for Windows I should be able to provide an installer for this system too.
From the website:
Pack My Sprites is a program that generates sprite sheets from a collection of images made with Gimp. The process does not requires the user to produce any intermediate image files. Thus, all you have to do is drawing the image and listing which layers to use for each sprite, then the program will generate the sprite sheet from it. Pack My Sprites makes the modifications on the source images costless for the project.
Are you intersted by this kind of tools? Would you be interested by a Windows version or a package for a given Linux distribution?