After years of lugging around a laptop case and a big camera bag, I broke down and bought a combination camera-laptop backpack - mine happens to be a Tenba. There are many pros and cons to buying one of these types of backpacks, so study up before making the investment --
• It will carry a lot of camera equipment (see below)
• It also holds my 15" laptop and some file folder, CDs, cords, etc.
• With it fully loaded I still have my hands free to grab things or hold airline tickets
• I can grab my camera, sling the pack on my back, shoot with both hands, and the bag never touches the ground (great when the ground is wet or muddy)
• The newer backpacks have wheels ... I'd like that.
• Don't buy the biggest backpack out there because many won't fit in an overhead compartment ... and they're really heavy!
• If you load it with too much camera equpiment, your back will hate you!
• If you travel internationally, access to your equipment is too easy for theft
• Some will easily hold a small tripod, others don't -- is that important to you?
Hope this helps you make a decision.