Good backpack for travelling?

I need a good, not too expensive backpack for studying abroad in Italy next semester. It should be good on my back, I don't necessarily need a laptop holder but it would be nice, ... and it should be big enough for maybe an overnight trip.
I'm a girl so if it's stylish that's a plus. Any suggestions from fellow travellers? Northface, Jansport, Swiss, any ideas?
:)

Go to a good sporting goods store and have them help you. It MUST fit you comfortably regardless what it looks like and those people know how to fit you for one that is usable.

What about the Deuter Grad II or the Deuter GoGo? I also like the Deuter Cross City, it will be very good if you need to take the bike to uni.

http://www.deuter.com/

Another good brand is Karrimor. I absolutely love their Arma packs - they look very stylish!

http://www.karrimor.com/urban.htm