Basebox-Packer
A comprehensive set of Packer definitions. It has quite a collection of 64 bit and 32 bit images for Vagrant VirtualBox and VMWare. A good place to learn Packer definitions.
linux open-source virt shell
Bento
A modularized collection of Packer definitions for building machine images. A good place to start with Packer.
linux windows osx open-source virt ruby