I don't have a backpack, but a shoulder bag from
Crumpler, specifically the
Breakfast Buffet. It is quite small, suitable for
"12" laptops" and smaller. Along with the laptop, it has space for a hardback book/ebook device in a cover, a charger or two, and some small stuff. You'd probably cram in more but (and, to get to my point) I bought it to avoid the whole "fill my bag to the brim" habit I had (which I suspect is the reason behind their naming of one of their bags the
Dreadful Embarrassment).
I like Crumpler, and they've a huge range of bags specifically for different uses (photography, messenger, luggage, laptop), including backpacks, but they might not be your cup of tea. My bag of choice has no kind of protection from the elements really (just a flap that folds over and velcros), though I believe a lot of them do (decent zippers, etc.).
All I'm really saying though is that if you're at all like me, then if you buy a
big bag you'll also find stuff to fill it. That can be a heavy habit.
So, if that's the case...well, the Breakfast Buffet worked for me, keeping my bad habit in check through necessity. If you don't consider it a bad habit, or you actually need all the stuff you put in it, and you're interested in the Crumpler stuff, well, you'll see the backpack options under Laptop at the
Crumpler website.
Cheers,
Marc