What Kind of Spider?

Can anyone tell us what kind of spider this is?

Dominic found it in our driveway last week. It was very big! I really don't like spiders at all and it gives me the shivers just looking at this picture. When he saw it, he made me come outside to look at it. Ever since then, Dominic has been trying to find out what kind it is. I sure hope it isn't dangerous because we have no idea where it is now. Just as long is it doesn't come in the house.

I was afraid that it was someone's pet that got away, it was that big.

Dominic is always finding something outside and has to show me. I like it better when he finds frogs. I can do without the spiders and snakes.

Please help us identify this spider.