I've just posted a pre-release of GIMP Portable 2.6.0 for testing. As this is a pretty major GIMP update, we're doing a test rather than rushing out a release.
Download GIMP Portable 2.6.0 Pre-Release 2 [16MB download / 16-42MB installed]
The GIMP Portable Background Window needed updating for this release as well:
Download GIMP Portable Background Window 2.1.3 Pre-Release 1 [0.2MB download/installed]
The Photoshop Layout should work as is but please test it.
Please test loading and saving of all supported formats as well as plugins.
Pre-Release 2 (October 8, 2008): Fixed errors in GEGL plugin, removed 2 unUPXable temp files from App\gimp\bin