I personally loooove Lightroom. It is great when you are editing a ton of pictures. The way the program is set up makes workflow very easy. It also allows you to still be creative. I also think it is important to have photoshop for when you want to go above and beyond. Lightroom is affordable as well. You can get for Macs or Pc's.
is there one for both? and it needs to be able to handle rawIt depends if you want Post Processing for touchups, or post processing for graphical work.
If you just want to do touchups, Adobe Lightroom is good. I use Aperture for the Mac personally.
I've never used GIMP, but I've heard good things about it (and it's free).