If you have done any Atmel / AVR development you have probably heard of Procyon AVRLib. If you haven’t, you are in for a treat. It is an old library, but contains incredibly valuable drivers for all manner of popular hardware and tasks.
AVRLib was written by Pascal Stang and he maintains a site here. The problem is that the site is not well maintained and often the library is completely unavailable.
I’m going to go ahead and maintain a mirror of the latest library package which you can download here at any time: Procyon AVRlib