Related thread over at the bah forum:

Here is a link that might be useful: mud

Since you don't have a large area you could use compacted crusher run. It could be made longer lasting by first laying down fabric.

Another method that I've heard being used to consolidate driveways on construction sites was to grade the area, then spread dry portland cement over the area, right out of the bag. Till it in the top few inches, then compact it.

No need to add water, the moisture from the dirt will cause it to hydrate.

Mongo

I was considering tilling in a bag of cement.

Anyone out there do this?

Whatever you put down eventually will probably need a decent base if you want it to last.

Put down some more gravel.

I would have it dug out to the depth of what it would
be for the final finished driveway. Then I would have
several inches of the crusher run spread on it. If it
is a wet or non-stable area, then a fabric first. Then
when you get ready to put on your asphalt, you will have
a good base and the work you did now will not have to
be wasted.

I think your best bet is to put a layer of geotextile fabric down and then some stone. The fabric will keep the soil from migrating into the stone and the stone will add to the base of paving surface when you get to it.

My 0.02.