What kind of spider is this?

Called a wolf spider, family Lycosidae. these are awful hard to peg genus and species from photos, but looks like a pretty Tigrosa species,maybe Tigrosa annexa?
I don't often see them with such contrast.
http://bugguide.net/node/view/825726/bgimage
Rather harmless but can bite if trapped against the skin. They are outdoor spiders, perhaps release your little friend in a garden or under some shrubs to reign terror on the bugs of the world.
You can find these at night with a flashlight because their eyes shine like cat eyes in a light. Note the two larger eyes, these hunt on foot and have some decent eyesight at night.
Make good pet spiders also.
Update:
No they won't harm your pets, might be like getting stuck by a rose thorn if they bite, that is the worst. I had the huge carolina wolf spiders and my dog would go sniffing them and sometimes get tagged on the snout, a bit of yelp, but I think more surprise than hurt.
Really takes a bit to get spiders to bite you:
https://www.youtube.com/watch?v=IYWzS8D8y0E

I'm going to guess that your spider is a wolf spider, family Lycosidae.

Note: I can't tell some of the wolf spiders from some of the genus Hololena funnel weavers without looking at the web, LOL.

Top answerer Daniel G will be along in an hour or two with the right answer. He's very good at pointing out differences in arthropods that seem to have a fair bit of convergence.

Look like what I used to call a Tunnel Spider. [I bet that is NOT scientific!]
They live in junk and piles of wood, even in the crack in the foundation of a house.

They build a tunnel that goes inside the crack or can or other opening behind them. On the front of the tunnel is a "porch"of thickly woven, very silky threads.

When an insect (I used to catch ants and feed them) lands on the porch, the spider run out, bites the insect, and then runs arpund in circles covering the insect with silk. Then they drag the "cocoon" back into the tunnel.

Their bite can be painful, but not deadly. And they tend to run instead of bite.