I recently found this info interesting:
Hidden Exposé Features
The Exposé blob is a hidden feature within exposé that sits on your desktop and allows you to invoke Exposé by clicking it.
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.
killall Dock
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.
killall Dock
I tried it and it is very simple to do.