It's called a 'title loan' - you put up the title of your car, they give you a fraction of it's value, and a hefty interest rate.
You have to have clear title on the car (no loans outstanding, etc), and a few other conditions need to be met. It's a step further down the road, beyond payday advance places...
Depending on where you are at, it may not be legal (to the best of my knowledge, title loans are no legal in Ontario)
Laz