The Red Paw Packs Flatiron Pack 28 L (13 to 19 oz / 368 g to 538 g, MSRP from $220) is a customizable low-volume overnight / daypack with a unique zippered main compartment.
Having accessible "pockets" on your pack is useful for keeping little bits of gear handy without taking off your pack. But consider a multi-use pouch that can also be worn as a standalone fanny-style pack.
The Drop 40L is a 30 oz (842 g), small-volume pack designed to make externally stored gear easily accessible while moving quickly.
The Osprey Lumina 60 Backpack is a sub-2lb, internal frame pack that is gender specific and found in outdoor specialty stores.
This REI Flash 55 Backpack review features a user-configurable, lightweight, internal-frame, roll-top pack.