I have a couple of image format plug-ins available for the GIMP one is included with the GIMP (pix) and one of them (formerly tdi, now MayaIFF) has been in the unstable tree since before 1.0 was released. The latest version, as always, is in the plug-in registry. It's not likely that many people on this list will be very interested in files of the MayaIFF variety. You would either have to be using Maya (http://www.aliaswavefront.com/entertainment/index.html) or Shake (http://www.nothingreal.com/). And would probably put you in the film or video game industry.
