Simple Event Attendance (SEATT) is a small plugin for WordPress 3 that allows you to add attendance polls to your posts/pages.
Simple attendance list, multiple lists can be added to any post or page and subscribed members can be edited.
Add an event in the admin panel with a name, description, closing date (for signing up) and registration limit (for number of users who can signup). You can then embed a form into any post or page using the wordpress shorttag (x = the event id).
From the admin panel you can read comments left by people who have registered, as well as boot them off the list or delete the list altogether.
For screenshots, more info and to download head to http://wordpress.org/extend/plugins/simple-event-attendance/