Leave the doors and windows open until it evaporates!

Doc

Try using cat litter.  It'll absorb some of the odor and what is left of the
gas.  After that, You'll just have to let it air out...

Get a new car.

Seriously, I doubt this will ever go away completely, and I think
it's probably quite a health hazard.  I don't think after a time if
you don't smell it, that it means its gone necessarily.  I'd think
about turning it in as an insurance claim.  If it was on the carpet,
or any fabric such a seats, those can be replaced.  On a non-pourous
surface it could be cleaned, but I don't think steel is even totally
impervious to gasoline.  I know one thing for sure, I wouldn't
breathe gas fumes if I could help it.

Soap ad water

Scott, I did this once before and used vinegar and it helped.  First try a
dilution of 3 parts water to one part vinegar.  Let it sit a bit then blot
the area to remove the liquid.  Keep at it and it will help.  You can go as
strong as 2 parts water to one part vinegar but I would not go any stronger.
Hope this helps!