Overclocking . . . try using Google, there are a lot of articles on how to do it and the benefits and drawbacks.
As mreeves said, it may shorten the lifespan of your CPU if you don't have good cooling in place.
But, it can improve performance significantly if carried out with care and patience, and can save you upgrading.
The CPU, RAM and graphics card can be overclocked but I don't think anything else can.