If you haven't taken a look at what you can do in Gmail with your keyboard lately, you may want to check it out. Though Gmail keyboard shortcuts have been around a while, new ones have been added periodically, coinciding with enhancements and new features.
Yahoo's Webmail service hasn't always had keyboard shortcuts, but the latest incarnation of Yahoo Mail does. We list some of the more useful ones for you.
Hotmail, like Gmail and Yahoo Mail, supports the use of keyboard shortcuts. The interesting part? You can customize them to mimic the keyboard shortcuts from Gmail or Yahoo Mail.