This module let's you manage event sign ups. Nothing special so far. I worked on it for a friends site (http://www.gatecamp.de) to manage the sign up process there.
Sources are available through subversion at https://svn.poldylicious.de/sign_up/.
I wouldn't recommend it's use just yet. Mostly it still is alpha status and it is tailored mostly at my friend's site. Comments are welcome though.