I have 6 film holders, a filter holder with 7 filters (#s 8, 12, 15, 25, 58, 81A, and CP) and 2 step up adapters, a couple pens, a spare pack of cigarettes, meter, loupe, small straight/philips screwdriver, zip strips, and steel clipboard. The clipboard holds my shot record, but has some laminated information. That information is light color, reciprocity information, a Planckian color chart, and my homemade filter/color chart. The filter/color chart shows the scale of colors from 430-720nm with the color gradient, and the data from the book on Wratten filter transmission for each range. This helps me decide what factor to use for each filter based on the color/wavelength and filter transmissions.
I use a laptop case for all that, and carry my camera separate. I only have 1 lens, so I don't need something to hold more. I'm not hiking far, or climbing mountains, so it's not too bad.