By Stijn Verwaaijen

Use a hotcorner to minimize all windows on current workspace

First of all, this 'hack' (or whatever you want to call it) has not been tested by the elementary team and is therefore not to be considered stable. On the other hand, I have not encountered any issues while using it.

For starters, we need a terminal. To open pantheon-terminal use the shortcut CTRL+ALT+T or open slingshot (WIN+SPACE), type "terminal" (without the quotes) and hit ENTER. Now, using your terminal, install a package named libwnck-3-dev.
sudo apt-get install libwnck-3-dev
Then click the following link and save it as a file called mimimize.vala.
Let's say you saved the file in your Downloads directory. Go back to your terminal, navigate to /home/[YOUR USERNAME]/Downloads (or ~/Downloads) and run the following command:
valac --pkg libwnck-3.0 -X -DWNCK_I_KNOW_THIS_IS_UNSTABLE minimize.vala
Finally, run system settings: open slingshot (WIN+SPACE), type "settings" and hit ENTER. In the category "Personal", click "Desktop". Now click the tab called "Hot Corners". Pick one of the four hot corners and set it to "Execute Custom Command". Put this in the box: /home/yourusername/Downloads/minimize

If everything worked out, you can now minimize all windows by pointing your mouse cursor to the hot corner that you chose. This can be useful for taking a quick look at your wallpaper, checking your conky or simply clearing your desktop so you can breath freely again when it gets a bit crowded.

By the way, this is no toggle; windows aren't restored when you move your mouse cursor to the hot corner again (just the way I like it).

To sum it up, not only did you add functionality to your window manager (gala), you did so by compiling vala code! This was a first for me and it certainly did put a smile on my face.

All credits go to +Tom Beckmann.