Microsoft
Microsoft: Keyboard Shortcuts for Windows
This reference from Microsoft lists the keyboard shortcuts you can use in Windows.
Other
Compu Kiss: Keyboard Basics
Computer keyboards have traditional typing keys (alpha, numeric, and symbol) in additional to unique keys with special functions. Learners will be able to explore the abilities of all unique keys that access the major keyboard functions.
Computer Hope
Computer Hope: Microsoft Shortcut Keys
Explains basic key terminology and computer shortcut keys (keyboard shortcuts), and lists shortcuts for these Microsoft applications: Windows, Excel, Word, Internet Explorer, FrontPage, and Outlook.