I know Tim has already bought a Brain Bag but if you have to carry around an SLR, a laptop, and other things (I also carry an iRiver, an iSight, 2 microphones, a zoom lens and many other technical doodads and geegaws), there is really no other alternative. It ain't stylish being all black but it does the job and it does the job well. Highly recommended.
From Lowepro - CompuTrekker AW.:
A perfect combination for photo gear and notebook computer, the CompuTrekker AW was designed specifically for digital photographers. Photojournalists and location photographers will find it a great travel companion. The backpack's reinforced construction, shock-absorbing closed-cell foam padding and tough, water-resistant outer fabric protects contents from moisture and sudden impacts. The patented All Weather Cover(tm) offers maximum protection from extreme weather conditions, dust and sand. A padded notebook compartment is secured with both zipper and quick-release buckle; while the main camera compartment is fully customizable with adjustable padded dividers. A quick-access hide-away Tripod Mount(tm), SlipLock(tm) attachment loops and a number of laminated and zippered organizer pockets provide photographers with fast, easy access to equipment.