I'm doing some programmer coaching and meant to suggest usecases.org (as usual) for a good source of use-case templates, but the site seems to be gone.

Or rather, the content moved to Alistair Cockburn's web site, and can now be found here.

The templates are as good as ever. My favorite one is (guess?) the plain text version, if only because putting it under CVS version control allows you to follow the diffs precisely.