Woopid is a great resource for Office 2007 and many other applications – both Mac and Windows. Check out their bundles at http://www.woopid.com/groups.php

I’ve only looked at the PowerPoint section, but it was an easy way to get up-to-speed on some fo the new features available in Office 2007 for Windows. (Not Keynote yet, but some nice improvements)

Tutorials are separated into short sections, most three to five minutes in length, so you can learn about a targeted skill/concept and then try it for yourself. Narration is well done, concise, and reassuring. The audio and visual quality are excellent.

I don’t know if the site will become a fee-based endeavor, but for now it’s a resource that you can recommend broadly. There are topics to help the beginning user, and enough depth to get even the most seasoned user a new skill or tip.