I have the Timbuk2 Outtawhack
http://www.timbuk2.com/tb2/products/outtawhack-day-pack#product=4-42549
Really versatile, great protection, just quirky enough, available in conservative colors, and my fave, has multiple carrying configurations: shoulder strap, backpack straps, and good ol’ handle. My only gripe- no place for water bottle. Otherwise, great bag. Holds my monster dell 17" a bit tight, but it fits.