Good ones I've come across (with useful comments):

https://github.com/sjl/dotfiles/blob/master/vim/.vimrc

https://github.com/cloudhead/dotfiles/blob/master/.vimrc

https://github.com/rtomayko/dotfiles/blob/rtomayko/.vimrc

https://github.com/nvie/vimrc/blob/master/vimrc

https://github.com/vgod/vimrc/blob/master/vimrc

https://github.com/spf13/spf13-vim/blob/master/.vimrc