Quickly preview Markdown documents from vim.
git submodule add git@github.com:mattgillooly/vim-markdown-preview.git bundle/vim-markdown-preview
git submodule init
nnoremap <leader>m :PreviewMarkdown<cr>
Download Markdown.pl from http://daringfireball.net/projects/markdown/ and put it in your ~/bin/ directory (or elsewhere, and update the Vimscript to aim correctly at it.)
No syntax highlighting or other Github-specific niceties.