What Caleb said.
Clean it all out, remember there are fines for pumping oil from the bilge and if you are in the US you need the bilge oil placard as well.
I'd suggest cleaning down the engine and transmission thoroughly, then at a minimum place clean newspaper all underneath the powertrain (tape it down) to try to see where the drips land. They can be coming from a rear main seal in the engine, in between the engine and gearbox where it is usually impossible to spot but that location also usually leaks only when the engine is running.
If you really want to chase it down...clean down the engine & tranny, dry it off, dust it with plain talcum powder. Anything that leaks and drips will create a path in the powder dust that is more easily seen.
You can also buy UV dye and a blacklight (same type used for rockhounds or AC testing), add the UV dye to the gearbox oil, and see if it shows up in the blige or under the powertrain. Give it a week, if the gearbox isn't leaking, add the same dye to the engine oil--and then see if that's leaving traces. There should be a clear UV stain down the engine (or gearbox) if that's where the leak in coming from.
Oilzorbs in the bilge, and under the engine, are a great idea in the meantime. Oil getting out with the bilge water can be a VERY expensive thing, and a 'zorb will suck most of it out of bilge water.