Most people are aware of the different application and window switching tricks in OS X, but real power in tools like Exposé and Spaces is when you start combining them and using them together to really save time.
Firstly lets quickly go through the different ways to switch between applications and windows. The most basic way is to use the keyboard shortcut Command-Tab to cycle through your open applications, and Command-~ to cycle through the open windows of the current application. On top of this, you have the three different options for Exposé: Show all windows (F9), show current application windows (F10) and show desktop (F11). Your function keys may be different if you have one of the newer MacBooks, or if you have changed them in System Preferences. Finally, there is Spaces (F8), which allows you to switch between collections of applications and windows that you have organised into workspaces.
Using some of these techniques simultaneously is a great way to save time. My personal favourite is combining Exposé and Command-Tab. Start by invoking Exposé for current application windows (F10). Once all your windows are shown, you can hit Tab to make Exposé cycle through showing windows for each application individually.
If you are anything like me, when you have applications running in lots of Spaces you occasionally lose track of things. If you have completely lost a window, a great way to find it is to first invoke Spaces (F8) and then Exposé for all windows (F9). First, all of your spaces will appear, then Exposé will rearrange all the windows in every space so you can see them all. You can still drag windows between spaces, and as you do, other windows will automatically rearrange so you can still see them all. And as always with Exposé, hovering your cursor above one of the windows will give you its name.
The best way to find out what combination tricks work best for you is to just try hitting the different function keys in different situation. If you find any other great time-saving combinations, let us know in the comments.
To enable the blob, enter the following command into the Terminal (Applications/Utilities) and hit return.
defaults write com.apple.dock wvous-floater -bool true
Now you need to relaunch the Dock, which contains the Exposé program. This can be done from Activity Monitor (also in Applications/Utilities) but it is much easier to just type the following into the Terminal and press return.
Now a blue blob should appear on your screen. Notice that it hovers above all other windows, and you can drag it about. It is semi-transparent until you put your mouse over it, when it becomes fully opaque. Now there are a few things you can do with this blob. Just clicking it will do the equivalent of hitting F10 - it will activate Exposé for all windows in the current application. Option-clicking is the same as F9, Exposé for all open windows. You can add in shift (Shift-Click or Shift-Option-Click) to make everything happen in slow motion, just the same as if you were using the F9 and F10 keys.
To remove the blob, repeat the above command but with false at the end.
defaults write com.apple.dock wvous-floater -bool false
As before you will need to relaunch the Dock for the changes to take effect.
methodshop.com has a great tutorial on how to customise the blob to be a different image. This isn't too tricky, and basically involves looking inside the Dock application and replacing two images. Mac OS X Hints has a great idea of a prank to play using the blob. By changing it to look like the Hard Drive icon you can really confuse someone.
defaults write com.apple.dock wvous-showcorners -bool true
You will need to type
killall Dockfor changes to take effect and repeat the command with
falseat the end to reverse it.
This final undocumented feature is part of the show desktop function that you start by pressing F11. Instead of moving all the windows off the sides of the screen, Exposé will now put all of your open windows into a small box that can be moved around the screen.
defaults write com.apple.dock wvous-olddesktop -bool false
This is arguably the most interesting hidden feature for Exposé, however, be warned that it has some bugs. After using the show desktop function, the front window can freeze. Mostly this can be fixed by pressing F9 (the show all function). Of course you have to do the usual
killall Dockcommand to make the changes happen and type the command again with
trueat the end to reverse it.
Once you have started exposé (by pressing either F9 or F10) you can cycle through your open applications by pressing the tab key. Each time you press it, the current application is hidden and the windows for the next one pop up.
As with most things in Mac OS X, the way to do things always turns out to be beautifully simple and what you would expect. As a result, pressing Shift-Tab cycles through the open applications in the opposite direction, just the same as if you were "tabbing" through anything on your mac.