IdeasOnUsingWiki

Here are some things you can do with your wiki:

Resource for new hires. Make a page for new hires so they know what to do. They'll love you for it.
A wiki itself is a great resource for new hires. Any new hire can just search the wiki to find the information they need. This is very powerful and dramatically cuts the time it take for a new person to come up and be productive.
Documentation for features.
Tutorials.
A better power point presentation. Not better in the "look at me i can do graphics" sort of way, but better in the "here's something useful that can be reused forever sort of way". Most ppts are write once read never documents. On wiki they can be fleshed out and linked to so they can stay useful and updated by the user community.
Results for tests.
Meeting minutes.
Home pages.
To do lists.
Proposals.
Forum for asking and adding questions.
What has changed content.
What's new content.
With a wiki that has a powerful macro feature you can display reports from the wiki and embed applications.