Most common question I get after presentations, is: “How do you add those spaces in the Dock?”. So to appease the crowd, run this in your terminal:

defaults write persistent-apps -array-add "{'tile-type'='spacer-tile';}" && killall Dock

This will add a spacer to the rightmost position in the Dock.

Look at those delicious spacers between the icons.

After being added, you can move the spacers around like any other app icon to get the groups you like, and you remove them by right clicking just like other Dock icons.