I'd start with the "house" brands of several outdoor companies. REI has long made good-quality packs at affordable prices, and a pack that bears out this reputation is the Morning Star 75. It has nearly 5,000 cubic inches of capacityenough for a week, reallya lightweight plastic frame that absorbs shock from the load, and lots of pockets for organizing gear. At $145, it's a steal. L.L. Bean's Katahdin ($149; www.llbean.com) is more or less the same size and has a really nicely contoured hip and shoulder belt setup.
From there, take a look at the packs from well-regarded companies who aren't necessarily seen as "premier" pack companies. Kelty make some fine, reasonably priced packs, for instance. One example is the Kelty Haiku ($180; www.kelty.com), which is a very cleanly designed back (not a lot of pockets and widgets) that uses super-tough fabric and a highly rated suspension system. JanSport's Tundra 80 ($170; www.jansport.com) fits in the same category as the previous three, and has access through both the top lid and a back panel.
Even some of the "premium" pack makers have become more price-conscious, building fine-quality packs with less bells and whistles than their flagship models. That said, Gregory's Forester ($239; www.gregorypacks.com) is a fine pack by any standards, with an excellent suspension and a rugged, clean design. Meanwhile, I'm trying Osprey's Aether 60 ($199; www.ospreypacks.com), which is a little smaller than the other packs here but seems ideal for fairly short trips. It's light and has great suspension. I'll tell you more when I've had more chances to use it.
Fit is important in packs, of course, so try to take the time to test several packs in a store. And do so with some weight in the bag20 pounds or so, enough to make the suspension sag a little so you can get a sense of how it will feel when loaded.