There are many products on the market designed to remove oil stains from driveways. Some of them actually work. The primary problem with them is that they basically dissolve the oil, much of it soaking even deeper into the concrete. That means you have to soak it up and attempt to not worsen the problem by spreading it out. Some of them will dissolve the oil, asphalt and all, leaving you with a bit of a hole where you used to have an oil stain. Generally, they're rather toxic. So the standard instructions are to soak up any oil you can with sawdust or rags. Then work from the edge of the stain toward the center, to limit the spreading of the stain.
It was inevitable that someone would come up with a better idea. It is called OIL LIFT. This non-toxic bio-degradable substance from British Columbia that foams the oil up out of the asphalt, brick or concrete and puts it into a water suspension where it will not stain the surface around the original spill or drip. It also begins a process of breaking down the petroleum based hydrocarbon chains, making this whole mess bio-degradable. Although you should soak up as much as you can, you can actually hose off the work without making more of a mess. You can even throw it on your grass rather than down a drain -- to the grass this all becomes a fertilizer. Although even this will not completely remove all stains (where was that driveway sealer before you dripped oil on your driveway?) it works as well or better than the traditional cleaners without the side effects of spreading the stain, eating the surface or polluting the environment worse than the oil.
It is a true ecological alternative to all those solvents - it even carries the Canadian EcoLogo seal. Not bad for a driveway cleaner. It is slowly becoming available in stores throughout North America, most easily found in Canadian Tire stores or check out www.OilLift.net.