Gitshame is now live at gitshame.xyz!
To use the command line tool copy the script into your path, for instance /usr/local/bin.
Then you can just call git shame /path/to/shameful-file.
To specify the shameful lines you can use git shame /path/to/shameful-file --start-line i --end-line j
where i and j are the line numbers describing the range of the shameful code.