Windows Vista offers a healthy assortment of keyboard shortcuts, which can often be significantly more efficient than mousing around to perform everyday chores. Scott Lowe has put together a PFD of the most useful shortcuts in Vista. Organized according to where you use them (desktop, Sidebar, etc.), the list encompasses the basics (locking your computer, launching Task Manager) as well as the more obscure (cycling through Sidebar gadgets, displaying system properties).
This is a good one to download, print out, and share with your users (or to keep handy for your own quick reference). If your favorite shortcuts aren't on the list, post a comment to let us know. We'll keep building out the list to include member additions.
Incidentally, if you're more interested in Windows XP at this point, you might want to check out "50+ keyboard shortcuts to move faster in Windows XP."