I keep the following in mine: 2 gallon gas can, 1 gallon bottle of wiper fluid, couple quarts of oil, 1 gallon of coolant, jumper cables, shaker siphon, a 2 quart water bottle, small lunchbox size survival kit, flashlight, insulated bibs and other misc. I think the bag's especially good for the price and like that it doesn't slide around and can be zippered up to look neat.

In the CR-V there's storage under the picnic table (!) where I keep a car charger/air compressor, a collapsible snow shovel, blanket, Fix-a-Flat, etc. I keep other items tucked in the various nooks and crannies around the car.