My biggish camera can take pictures in RAW format. This means that rather than compressing and processing the image data when it takes a picture, the camera simply dumps the output of the photo sensor into a file. It results in rather large files (around 14Mb in my case) for each picture but it does represent the epitome of quality, as you get all the data from the picture. It also means that you can do things like white balance compensation (making sure that things don't look yellow, or blue or whatever) after taking the picture, rather than at the time.
I was taking pictures of Seoul at night, and unsure about the white balance, so I took a few RAW pictures as well. The bad news was that when I got home, I now had to convert them into proper images. Fuji, who made my camera, supply a truly horrid set of programs to do this. They don't work very well on Vista, and I've lost the disks, so I thought I was stuffed. Until I found this.
These folks have written an image decoder for Finepix cameras that does everything I want. It is free and it works. If you want to play with RAW images and get the maximum quality from your camera, you should download the program and have a play.