Desktop shortcuts edit

Activate Menu bar Ctrl+Fn+F2
Undo the last operation ⌘ Cmd+Z
Redo the last operation ⇧ Shift+⌘ Cmd+Z
Cut the selected area and store it in the clipboard ⌘ Cmd+X
Copy the selected area into the clipboard ⌘ Cmd+C
Paste contents of clipboard at cursor ⌘ Cmd+V
Select everything in focused control or window ⌘ Cmd+A
Toggle between installed keyboard languages ⌘ Cmd+Space

(This may already be mapped to 20pxSpotlight Search)

Text editing edit

(Use these while holding ⇧ Shift to select while moving)

Start of line ⌘ Cmd+
End of Line ⌘ Cmd+
Start of Document ⌘ Cmd +
End of Document ⌘ Cmd +
Previous Word ⌥ Opt+
Next Word ⌥ Opt+
Previous line break ⌥ Opt+
Next line break ⌥ Opt+
Search ⌘ Cmd+F

Web browsers edit

Bookmarks Menu (Firefox) ⌘ Cmd+B or ⌘ Cmd+⇧ Shift+B
Bookmarks Menu (Chrome/Safari) ⌘ Cmd+⌥ Opt+B
Add a Bookmark for the Current Location ⌘ Cmd+D
Prepend "www." and append ".com" to a URL (Chrome) Ctrl+↵ Enter
Prepend "www." and append ".com" to a URL (Firefox) ⌘ Cmd+↵ Enter

Go menu edit

Go to the previous location in history ⌘ Cmd+[ or ⌘ Cmd+
Go to the next location in history ⌘ Cmd+] or ⌘ Cmd+
Go up/down one level in the navigation hierarchy ⌘ Cmd+ /

Text formatting edit

Make selected text bold/regular ⌘ Cmd+B
Toggle underlining of selected text ⌘ Cmd+U
Make selected text italic/regular ⌘ Cmd+I
Change to upper/lower case ⌥ Opt+⌘ Cmd+C

Window management edit

Switch Applications ⌘ Cmd+(⇧ Shift+)Tab ↹
Switch focus to the next/previous window ⌘ Cmd+(⇧ Shift+)`
Close the focused window ⌘ Cmd+W
Minimize the focused window ⌘ Cmd+M
Minimize all ⌘ Cmd+Alt+M
Switch to next/previous desktop Ctrl+/ (10.5 or later)
Show/Hide desktop Fn+F11
Quit Application ⌘ Cmd+Q

Tab management edit

Create new tab ⌘ Cmd+T
Close current tab ⌘ Cmd+W
Go to next/previous tab (Chrome and Firefox) ⌘ Cmd + ⇧ Shift + {/}
Go to next/previous tab (Safari) ⌘ Cmd + ⇧ Shift + /

Desktop navigation edit

Open/Run a File/Application Cmd+O
Save a Screenshot to the Desktop Cmd+Shift+3
Save a selected area Screenshot to the Desktop Cmd+Shift+4

(When a crosshair icon appears, click and drag)

Save a Screenshot of a Window to the Desktop Cmd+Shift+4 (release keys) + Space

(When a camera icon appears, cursor over the window and click)

Application Force Quit Dialogue Cmd+Opt+Esc
Rename file Return