That looks to me like one of the Fall Dandelions. Does it get many stalks of small yellow flowers?

There are no flowers as of yet. I took another picture with a glove next to it for scale.

I looked up fall dandelions, and it looks like it could be it, but it's not a perfect match.

These do not have tap roots. They have very big horizontal roots running out from them.

Forgot to include the link to the picture:

http://www.flickr.com/photos/28666955@N08/2877554344/

To me, the leaves look fuzzy, the edges armed with prickly thorns.

If so, I'd say it's a thistle.

Looks like a thistle to me too. If it has large roots running horizontally, it would be one of the perennial thistles and you don't want to let it get started. Chop off or pull every one you see before it gets established or you will have years of herbicide application ahead of you to get rid of it.