A while ago I was pointed at Noise Ninja which is a great program for reducing picture noise. While investigating, I found a few other options, but no open source options. Looking at it again today I found that there are a few plugins for The GIMP in the works: most notably Dcam Noise 2, but also ISO noise reduction. I wonder what's keeping the open source world away on this, but I'm glad to see someone's working on it at least. At the moment I'm just adding a bit of blur to my images using GIMPShop and *shriek* iPhoto 5