You don't say what computing platform you're on. If Windows, I'd highly recommend Picture Window from Digital Light and Color. It's very intuitive for a photographer, powerful, has great features, and comes in pro and regular versions for about $50 and $90. I was offered a digital editing/retouching job on the spot in 2000 when I dropped off an image I'd edited in Picture Window to be printed. Picture Window is programmed by Jonathan Sachs, who wrote Lotus 1-2-3. I've been using it for at least 8 or 9 years. The new version does RAW file reads and batch processing.
The GIMP is avaialble for free for OS-X, Linux, Unix, and Windows. An offshoot of the GIMP (which is currently maximum 8 bits per RGB channel) named Cinepaint allows 48 bit image editing and is used by major studios for film editing. There's a list of films it's been used in on the home page. I have it running under Linux. It's free like The GIMP.
There is a hybrid version of The GIMP which provides the functions in a more Photoshop like layout, but I haven't bothered with it since I've always used Picture Window or the GIMP, and never felt the need to load any of the forms of Photoshop that came with scanners, etc.
Some good GIMP tutorials showing equivalent techniques to some Photoshop methods are here:
http://www.gimpguru.org/
I also use Vuescan under both Windows and Linux and highly recommend it.
See a short tutorial on using The GIMP for digital negatives here:
http://www.alternativephotography.com/articles/art026.html
Lee
http://dl-c.com
gimp.org
www.cinepaint.org