The shelf life of your olive oil can be prolonged if you add a little sugar in the bottle.
If you want your pesto sauce to keep its nice green colour for a few days in the fridge, you can cover it with olive oil.
Here is a tip for pizza lovers. Mix some olive oil with enough flour to make a very thin paste. Brush your pizza pan with this mixture, and then place the dough on top. This will make the underside of the dough nice and crispy.