Be aware of people who are going on vacation. There mind may shut down early leaving you room to take over and show what you are made of. You might be able to move just a little bit ahead of your co-employees by proving you can take over their work in their absence.
Vacations are sometimes very much needed but can set you back in some instances. If multiple people are gone, then it makes you look like your in charge of the office. You can start to make a name for yourself amongst other people you never deal with.