Software and Tips for Astrophotography?

Neotrantor asks: "I'm a college student in an advanced astronomy class and i need to find out how nasa compiles all their little pictures into those big pretty ones like the hubble deep field. does anyone know what software they use or where i could find it. furthermore, is it an operation that any kind of workstation (sparc, alpha, x86, g4) when left on and trashing for a while, could get the job done?" As I understand it, Picture Window (and the Professional version) have become valued tools in the amateur astrophotography world, what other pieces of software would aspiring Astrophotographers find useful in their toolkits? What other tips and trickscan you use to produce stunning visuals of the sky?