The post processing I do on my photos is limited to sharpening, saturation and simple contrast adjustments in Picasa. I was looking for software that gave a little more control (curves adjustments and unsharp mask for example). Photoshop is the popular choice, but the pricing (600$) is beyond reach. I used GIMP (on Linux) for a while, but its speed is frustrating. It was then I came across Picture Window Pro. Costs 90$ and the download size is a mere 5MB (300MB for the Photoshop trial). It does almost everything that Photoshop does (at least whatever you'd want for post processing photos). Head to IMAGEs by DEN to see what it's capable of. Check the before and after comparisons by moving the mouse over the images on that page. It not only convinced me about Picture Window Pro but also about the importance of post-processing.
Picture Window Pro runs smoothly in Linux with Wine. I ran the installer with the default Wine settings. I only had to copy gdiplus.dll from my windows partition to my fake windows directory to run it. It's much faster than GIMP and more stable than the Linux version of Picasa. I'll be trying it for a month before deciding whether it's worth buying.
Oh, and do checkout some stunning night photography at Cambridge in Colour.