Pretty simple since I start most of my drawings with a grisaille underpainting, I only pack gray and black pencils. I also toss in a small sharpener, an eraser, Bristol board paper precut to the standard 2.5 x 3.5" size and a selection of reference photos to work from. I keep the paper and photos in a small zip lock to keep them clean. It all fits in one of the newer Prismacolor tins.
Having this kit in my usually way-too-big purse keeps me drawing all the time since I have no excuses. Now if Cameron could just drive himself to all of those appointments, I could draw in the car, too.
Nah, I get carsick.