For day hiking I use the Lowe CompuRover AW. Since this also carries a laptop, it doubles as a travel backpack and is OK for carryon. It holds just about anything I would be willing to carry on an all-day hike, and the top compartment holds basic hiking supplies -- rain gear, lunch, etc. I even used it on an overnight bivy on a mountaintop -- it will hold a sleeping bag, and dinner.
For backpacking I use the same pack I would use for any extended hike (a Six Moon Designs Starlight). I use a Think Tank Holster strapped to the left side of the hip belt and a LowePro single-compartment belt pouch on the right side. The former holds the camera and lens at the ready. The latter can hold one, and sometimes two, additional lenses, a Cokin holder, two rings, and three 4 x 4 filters. All of these are within reach without dropping the pack. The tripod sits in a side mesh pocket (secured with an extra strap), and silnylon bags hold a pano bracket, spare batteries and other misc.
I also use the same belt pouch system for the CompuRover.