You need a special RAW converter. You camera should actually come with one. If not there's some packages like Adobe Lightroom which can read RAW files.
Heres some others. Ignore the version numbers it's an older list.
Bibble Pro v4.9d
Helicon Filter v4.5
Silkypix v3.03
DxO Optics Pro v4.1
Silverfast DCPro v6.5.0r3a
LightZone v3.0
Raw Therapee v2.1.1
ACDSee Pro
I don't know of any plugins for GIMP that could do it though.
There is a DCraw plugin for GIMP, which essentially uses "dcraw.c" to handle the RAW file processing. I'm using the following for my RAW file conversion:
dcraw.c
( for command line processing of raw files that I don't need special processing for, or if I just want bulk 16bit/channel linear TIFF(s) ) (usefulness is lowered, in my mind, since you lose the exif/iptc info that the camera embeds in the raw file.)
BibbleLabs Pro
Love this program. Handles RAW preview, image curves, etc. Allows you to bulk or singularly manage image changes. Great program. The only downside to this program si that the previews may not necessarily always reflect what the final image will look like. I've gotten previews that looked great, but the final result was heavily grainy and blotchy.
Adobe Lightroom
Adobe's RAW processor and content management system. Nice. Integrates with Adobe Bridge and PS.
Apple Aperture
Apple's RAW/content management application. Nice and continually being evolved.
Some of the manufacturer RAW converters for their cameras have special functions, like the dust removal feature in Canon 1D MKIII