Macintosh OS X command line to format a "man" page and open in the Preview application
groff -man /usr/local/git/man/man1/git-config.1 \ | open -a Preview.app -f
Update: Using the man -path argument you can further enhance the command line, eg
groff -man $(man --path git-config) | open -a Preview.app -f
Update 2025-6: Preview lost its ability to render PostScript so you now need to tell groff to output PDF: groff -Tpdf .... Man no longer supports the --path option so you would need to use something like
find $(manpath|tr ':' ' ') -name git-config.1
