On this Photoshop tutorial, Jesús Ramirez (from the Photoshop training channel) takes a look at creating a look known as the Dragan effect (sometimes also referred to as the 300 effect).
Named after Polish photographer Andrzej Dragan whose works has very high contrast and color style and create a strong dramatic look with a bit of HDR-style. If you are unfamiliar with this look you can find many examples with a simple Google search.
For those who are familiar with it, there is a good chance you came across similar grungy effect on movie posters and advertisements (Nike for example used something very similar quite a few times recently as Ramirez notes correctly).
Ramirez takes a look at how you can create this on Photoshop CS6 and above but also has a way of achieving a similar result for users of CS5.
You can find many more Photoshop video tutorials on LensVid’s Photoshop section.