When there's not enough light there's not enough picture information either.. so there is only so much you can do before it just looks like a mess.
First thing to try would be a gamma adjustment, and then some general color correction. You're probably going to have to live with it being a bit dark and chalk it up as a lesson learned -- Digital Video needs a lot of light.
So often, just setting your whites and blacks will improve the look of your (our) shots.