Emacs on Mac OS X Leopard key bindings

For reference, here are the key bindings, for moving around text:

⌥ + ← - move left one word
⌥ + → - move right one word
⌥ + delete - back delete one word
Shift + ⌥ + delete - foward delete one word
⌥ + ↑ - move up one paragraph
⌥ + ↓ - move down one paragraph
⌘ + ← - move to start of current line
⌘ + → - move to end of current line
Shift + any of the above extend selection by appropriate amount

Click then drag - select text
Double-click then drag - select text, wrapping to word ends
Triple-click then drag - select text, wrapping to paragraph ends

Shift + Select text with mouse - add to selection (contiguous)
⌘ + Select text with mouse - add to selection (non-contiguous)
⌥ + Drag - select rectangular area (non-contiguous)
⌘ + ⌥ + drag - add rectangular area to selection
Drag selection - move text
⌥ + drag selection - copy text

Ctrl + A - move to start of current paragraph
Ctrl + B - move left one character
Ctrl + D - forwards delete
Ctrl + E - move to end of current paragraph
Ctrl + F - move right one character
Ctrl + H - delete
Ctrl + K - delete remainder of current paragraph
Ctrl + L - center the window on the current line
Ctrl + N - move down one line
Ctrl + O - insert new line after cursor
Ctrl + P - move up one line
Ctrl + T - transpose (swap) two surrounding character
Ctrl + V - move to end, then left one character
Ctrl + Y - paste text previously deleted with Ctrl - K

Add Option to Ctrl + F or Ctrl + B to move a word instead of a character at a time.

The other answer was very complete, but additionally I'd mention I just set the caps lock key to a second control key instead of swapping them.

Also, you'll notice that the large majority of the text entry fields in Mac OS X already accept emacs keystrokes (^A beginning of line, ^E end of line, ^P, ^N, ^K, ^Y, etc)

good luck

Swapping CTRL and CAPS LOCK

1. Go into System Preferences
2. Enter the Keyboard & Mouse preference pane
3. In the Keyboard tab, click Modifier Keys...
4. Swap the actions for Caps Lock and Control.

Using ALT/OPTION as META

1. In the menu bar, click Terminal
2. Click Preferences...
3. Under the Settings tab, go to the Keyboard tab
4. Check the box labeled Use option as meta key

That's it! You should be well on your way to becoming an Emacs master!