Using a computer with no mouse isn't as hard as you think... if you think it's hard. Pretty much every program has shortcut keys, as well as windows itself, and they pretty much do everything. Obviously you lose a few features like being able to draw stuff and play certain games.
Here's the thing: Using the mouse requires you to move it, and the bigger your screen, the more you have to move it to get to places. Think of those massive 30" Apple HD Cinema Displays, the distance between the menu bar and the dock is outrageous. The cursor has to pack a suitcase and padkos before it goes on it's vacation to South Desktop.
The keyboard, however, has not changed its basic size since it's conception due to the fact that the human hand has retained its overall dimensions. Moving your hand across the keyboard to reach a certain key can take split-seconds.
Some of the first keyboard shortcuts were introduced by Apple, of course because they are like the king of user interfaces. Here are some of the most used Command (or Apple) Key shortcuts:
+Q quits the current program (like totally quits it)
+W closes the current window (doesn't quit the program, though)
+T opens a new tab in Safari, Firefox, Chrome.
+Space opens a quick search with spotlight.
Shift+Command searches through menu items.
+Z undoes what you just did (resembles the action of striking out a mistake)
(+X cuts the currently selected text/item (resembles a scissors) basically like copying and then deleting the original) This has been removed from Mac OS
+C copies the currently selected text or item
+V pastes the currently copied or cut text or item (resembles an arrow pointing downward "into" the document/folder/whatever)
Although some of the letters have some sort of "meaning", isn't it oddly coincidental that all of these keys are in one continuous line right next to the Command button? meh...
Windows computers have their not-so-all-powerful Windows Key (or WINKEY, which is a pretty bad name depending on how you read it). Now that I think about it, the Windows Key is probably the least used function key on the keyboard, for the average computer use that is. Here are some of them.
Just by itself it opens the start menu
+D shows the desktop, press it again to bring all your windows back.
+M minimizes all windows.
+Shift+M unminimizes all the windows you minimized with the previous shortcut.
+R opens the run dialog.
+E opens an explorer window at "My Computer".
+F opens a search window.
+Tab cycles between taskbar items.
+Shift+Tab .smeti rabksat neewteb selcyc
+L locks the computer.
+U opens the utility manager, for stuff like the magnifier, Microsoft Sam's annoying text-to-speech and the the on-screen keyboard.
+Pause opens System Properties.
Windows 7 added a bunch more:
+1...9 opens or activates the first nine programs on the "Superbar".
+G cycles through desktop widgets.
+Arrow Keys manipulates the size and position of the active window. Play around with it, you'll get the idea.
+Home minimizes all but the active window.
+Space makes all the windows transparent (like mousing over the "show desktop" button).
+Tab doesn't do the same as XP, but rather activates that silly Aero Flip or whatever it's called.
+T does what WIN+Tab does in XP.
+B switches focus to the system tray.
+Plus zooms in
+Minus zooms out
Not to mention all the useful shortcut keys that don't use the Windows Key:
Alt+F4 is everyone's favourite, isn't it? Easy to use, it has one basic function: Quit! It also brings up the Shut-down dialog when only the desktop is visible (like when you've quit all your programs with it already! Muahahahaha!!)
Ctrl+Esc opens the start menu. I only ever used this on an old IBM laptop which didn't have a Windows Key, which is very frustrating since I rely on so many Win+ shortcuts...
Alt+Tab switches between windows. In Windows 7 and some Linux distros, all other windows except the one selected will be visible.
Alt+Shift+Tab .swodniw neewteb sehctiws
Alt+Enter does different things depending on the program. In explorer and Internet Explorer, it displays the properties of the selected file or webpage respectivly. In most games it toggles full-screen/windowed mode (e.g. Far Cry 2, DOSBox, etc.)
Ctrl+T opens a new tab in Internet Explorer, Firefox, Chrome, Safari, Opera, etc...
Alt+Space is like right-clicking on the title-bar.
F1 for help.
F2 renames selected file.
F3 for finding stuff, like words in documents and webages. Also "Find Next" while you are finding something.
F4 aciates the menu bar of a window. Windows Explorer, Internet Explorer and a few other programs have the menu hidden, F4 shows it. The Alt key by itself does the same.
F5 reloads/refreshes the page.
F8 opens Windows boot options (like Safe Mode, etc) when pressed during Windows boot.
F11 makes Windows Explorer, Internet Explorer, Firefox, and other web browsers full screen, otherwise known as 'Kiosk' mode.
And don't forget that little key which opens the right-click menu. I find it very useful sometimes.
There are still hundreds more useful (and useless) shortcuts out there. Most are for specific programs (like the "F" keys in Corel Draw)
However, you are by no means limited to these shortcuts alone. There is an amazing utility called Autohotkey which allows you to create your own shortcuts for literally anything on your computer. It goes beyond keyboard shortcuts, as it also has features for the mouse and joysticks.
Let me know if there are any common, useful shortcuts I missed out. I have a feeling I've missed at least one very important one. lol
I would post some of my Autohotkey scripts, but my computer with all of them is broken. I promise to post all of them when it's up and running again.