Shift+Ctrl+Eject turns off the display(s).

You can tell at a glance when a document needs saving. A black dot appears inside the red Close Window button.

When you have the Save File or Open File dialogue open in Finder, press the / key and you'll get a dialog to type in a path.

You can use Spotlight from the command line using "mdfind".

While lots of Mac users know you can take a screengrab by using Cmd+Shift+3 (whole screen) or Cmd+Shift+4, not so many know you can save one directly to the clipboard using Cmd+Ctrl+Shift+3.

Many OSX dialogs accept emacs keystrokes for navigation, give these a try in the address bar of your browser:

ctrl-a - put cursor at beginning of line
ctrl-e - go to end of line
ctrl-w - delete the word to the left of the cursor
ctrl-k - delete everything to the right of the cursor
ctrl-u - delete everything on the current line

These commands also work in terminal (along with many others) and after some use, you'll quickly wonder why you spent so much time navigating around without them.

My favorite, least known keyboard shortcut:

Option + Shift + Volume Up/Down will increase/decrease your volume by 1/4th of the normal amount. (Total of 64 increments)

http://grab.by/2v2M

Also, Shift + Any volume button will silently perform the action.

A lot of the Universal Access features are ignored because people think they're for specific handicaps, but some of them are pretty useful for anyone. My favorite, and I'm pretty sure it's enabled by default, is to use Ctrl+Mousewheel to zoom in and out.

There's a hidden System Preference Pane ^[1] that lets you customize settings for decompressing archives located in: "/System/Library/CoreServices/Archive Utility.app/Contents/Resources/Archives.prefPane"

Similarly, there's Disk Image Pref Pane tucked away here: "/System/Library/PrivateFrameworks/DiskImages.framework/Versions/A/Resources/DiskImages.prefPane"

Control-click on the title (the current location) in the Finder to bring up a menu that allows you to select the parent folders.

At the Login Window, type ">console" to exit to command prompt. Link ^[1]

Hold Opt+Cmd and click an app in the Dock to show that app and hide all others.

While in Terminal, execute "open ." to open the current location (path) in Finder.

There's some menubar extras ^[1] hiding in: "/System/Library/CoreServices/Menu Extras/"

Holding Cmd while clicking often reveals (opens Finder and selects) instead of opening. E.g. Cmd+clicking a Spotlight search result, or a Stacks folder, or a file in an expanded Stacks folder.

While command-tabbing between applications (and still holding down the command key) there are a few handy shortcuts...

• H will hide the selected application
• Q will quit the selected application
• ← and → move the selection
• ↑ or ↓ switch to Exposé on the selected application
• Just as Tab goes right, Shift-Tab and tilde (~) go left
• Moving the mouse over the switcher moves the selection
• The mouse scrollwheel will also move the selection

The mac comes with a graphing application called "Grapher". Nice GUI.

Option + maximize button for when you cant see the lower corner of your app(itunes especially)

Ctrl+Option+Command+8 will invert the color of your screen. On my old powerbook it switched it to b/w too, but the newer hardware/software keeps somewhat of the color.

the services menu and the dictionary. you can type dictionary words into spotlight, or highlight a word & go to Application-->Services-->Dictionary

Just like in NextStep Days!!

In each textfield of Cocoa Application (i.e., Safari, Mail, ...), you can call the Spelling and Grammar checker with :

Command + :

When dragging from one Finder window to another:

• with no modifiers, you'll move the file [provided source and destination are on the same volume].
• hold down Option to copy the file. [You'll see a big green plus cursor.]
• hold down Command-Option to make an Alias (or shortcut). [The cursor will be a curved arrow pointing backwards.]

I made a folder called "Shortcuts" and put Aliases to folders I work with all the time, and put it on the sidebar in my Finder and as a folder on the Dock.

Force Quit an application ^[1]: hold option key down after you ctrl-click on an application in the dock and the context menu will show "Force Quit" in place of "Quit"

cmd-option-eject instantly puts your mac to sleep

When you have a document open, the icon at the top of the window is more than just a picture. You can file most documents in a different folder by dragging their icon from the top of the window into a Finder window. Unfortunately there are some major apps like Microsoft Office 2004 where this doesn't work

on the command line, open path/to/some/file opens the file in its associated application. Very handy also for directories (even if hidden).

edit: As "Antony Perkov" says in the (hidden) comment hereafter: "You can also use "open -a application file" to open the file with a specific application."

Snow Leopard only: you can see and open invisible files (hidden files) from an Open or Save dialog box by pressing Command+Shift+. (the Command and Shift and Period keys)

You can drop a file in Open and Save dialogs to change the current directory.

Very useful if you already have a Finder window displaying where you want to open/save.

• Ctrl + mouse scroll wheel: Zoom in/out (Nice when doing CSS/gfx or when Flash videos don't support fullscreen)
• Cmd-D in Save/File-dialogue: Go to Desktop
• Type open . in Terminal: open current folder in Finder
• Hold Cmd while dragging a window: Drag it without bringing it to front
• Cmd-click on title in most document-based windows (inc Finder): Show drop down with path tree from here to root
• Hold Opt while resizing the dock: Snap to predefined icon sizes (less on-the-fly rescaling work I guess)
• Ctrl-Cmd-D with the mouse cursor over a word in Safari: Get a quick in-browser dictionary lookup
• Cmd-drag the little icons in the menu bar: rearrange them (Not spotlight though)
• Cmd-drag standard tool icons in windows: rearrange them
• Click-hold on the little icon in Finder window title for ~1sec and then drag to Terminal: Pastes the absolute path of that folder. (Very useful for cd to/some/folder)
• Cmd-Opt-I after selecting multiple items in Finder: Get up one window with accumulated information
• Click on any menu to make it show, then hold different keys like Cmd, Ctrl etc: Show alternative commands (for instance try Finder › File and then hold Opt or Shift or Ctrl)

Edit:

Oh yeah, just gotta do this edit, as you can seriously not live without these:

• Up/Down arrow in Finder: select next/prev folder/item
• Cmd-Down arrow Finder: Go into folder or open item (Hold Opt to hide 'old' window if in minimized mode.)
• Cmd-Up arrow in Finder: Open parent folder (hold Opt to hide 'old' window if in minimized mode.)
• Cmd-1 or 2 or 3 in Finder: Switch view mode
• Left/Right arrow in Finder: Expand/Contract folder (when i view mode 2)

If you've got a bunch of windows open in Finder, holding down the Option key when clicking the close button on one window will close all of the windows.

You can use the Script Editor "Get Result of AppleScript" service to execute shell commands most places you can put text.

E.g. if you type:

do shell script "ls -l /"

Select it and hit cmd-shift-8 (i.e. cmd-*) - which is the shortcut for the "Get Result of Applescript" Service it will run the "ls -l /" command and put the output where the "do shell script..." text was.

I often find this useful when generating documentation.

There used to be a Service from a 3rd party developer that let you do just that without even needing the "do shell script", but I've not been able to locate it. Love to hear about it if you know where to find that Service.

There are some caveats with the AppleScript do shell script command itself - you can see them here: http://developer.apple.com/technotes/tn2002/tn2065.html

At the login window, you can also type in ">restart" and ">shutdown", and both do as you'd expect (provided the system hasn't been configured to ignore them.) [I can't find a reference for them, but I beleive they are correct.]

There's a " Unicode Hex Input ^[1]" keyboard method in the International System Preference pane. Very handy if you ever need to enter a lot of unusual characters by their character code ("zero-width space", anyone?). Eg: Select "Unicode Hex Input" as the layout, then hold Shift+Alt and type 2614 and you'll get the umbrella character.

holding option (alt) key while clicking on the maximize button (green) resizes the window's height to the space between the Dock and the top menu bar.

AddressBook -> "Large Type".

Besides being an obnoxious kind of "I use display postscript!" kind of NeXTSTEP-ish feature, it must have been created by someone that actually uses their own software product.

In most applications (including Finder) you can move between multiple open windows by holding down the Command (Apple) key and tapping the tilde key (just below the escape key, to the left of 1). And if you hold down the shift key while doing this it reverses the order.

This feature can be disabled in System Preferences / Keyboard & Mouse / Keyboard Shortcuts.

Password Assistant exposes Mac OS X's built-in configurable password generator.

http://www.pcworld.com/businesscenter/article/187397/password_assistant_exposes_builtin_os_x_password_generator.html