To install via Git:
cd ~/"Library/Application Support/TextMate/Bundles/"
git clone git://github.com/jsallis/nuspec-tmbundle.git "NuSpec.tmbundle"
osascript -e 'tell app "TextMate" to reload bundles'
Source can be viewed or forked via GitHub: http://github.com/jsallis/nuspec-tmbundle/tree/master