LapTrap, which is a backpack with shoulder strap and mesh backpack strap. It's extremely light and everything fits comfortably in this case. Several zipped pockets and an excellent LapTrap for working on my BlackBook 2.4 while on the bus or train as I commute to and from campuses. It also sits up above the bottom of the case by about 3/8" rubber pads that are adjustable, so your BlackBook can BREATH. About $55.00 plus tax, everyone is always asking where I got so I send 'em to this website:
http://www.highergroundgear.com/laptrap.html
I actually visited their booth at Macworld SF '07, and it was well worth the money!
😎