No one suggested oil speedy dry? (I did see someone said kitty litter).
If you don't want to buy a bag, stop by your local auto garage and ask if you can have a coffee cans worth of speedy dry.
On fresh oil that's sitting on the surface you just need to cover it with oil dry and let it soak it up...then just sweep it away.
For old oil stains you'll want to let the oil dry sit on the concrete for a while...the longer the better. You can also "mash" the oil dry with your foot to break it up on the concrete. We used to do this in the farm shop...let it sit a day or two and then sweep it up.