Dynamic images resizing
Well, for resizing it would of course be better to use GD... But indexed, I think. So that you have an upload script that automatically generates the images' in other sizes, and saves them somewhere.
However, it matters whether you have more disk space, or performance... Performance would get worse IF you have many people viewing these images. Disk space would get worse IF you have A LOT of these images.
I'm working on project where we are trying to adopt and resize template images to the various resolutions. For example if the website is viewed in 800px width (800x600) and 1024px width or larger the image size should be viewed in same quality. 
I've had in mind to use sprite with 3 types of images for each range of this template , but I'm looking for other ideas , php gd maybe ? Any python solution ?