melmac is a tool for translating C programs into ALF. If that doesn't mean much to you, you are probably not a potential user :-)
melmac's documentation is not very extensive, but then again, there is not so much to say about it. Currently, the most informative document is the README.
You can browse melmac's sources here: http://www.complang.tuwien.ac.at/gergo/melmac/repo/melmac/.
That directory is also a darcs repository. It always contains the most up-to-date version of melmac. You can keep updated on the newest patches by using the darcs revision control system yourself.
Here's what to do once to get a copy:
> darcs get http://www.complang.tuwien.ac.at/gergo/melmac/repo/melmac/
And this is what you can do (inside your repository) from time to time to get new updates:
> darcs pullThat's it!