REI Men's Venturi 30 Pack

I've gone through 4 daypacks in 9 years, and this is the best one by far.

The size is just right, not big like a multi-day pack, not small like a race pack.

The "trampoline-mesh", raised separate from the back panel, provides the most effective ventilation I've experienced due to the free-flow air feature. Water-proof zippers ensure nothing gets wet in the rain, and compression straps ensure no movement of your load.

The hipbelt transfers most of the load to your hips and off of your shoulders, but the shoulder straps are so comfy and supportive that even if your shoulders need to take some weight, they'll still be comfy.

I'd love some internal organization pockets, and some lower compression straps would be nice, but that's just nit-picking.

Bottom-line, great pack for a killer price.