In a recent entry on the Google Analytics blog, Nick Mihailovski published that GA now offers event tracking. After doing some setup like adding categories to your GA account, this works by simply calling the Javascript function _trackEvent:
trackEvent(category, action, optional_label, optional_value)
Since this can be called in any context, it allows you track something standard as downloads, but for example also whether your fancy drop down menu is actually used.
For details about this, see the documentation on google code or a tutorial. Actually the mentioned tutorial is from 2007 – at this time the functionality wasn’t available to all accounts. It should still be valid though.