Recommended daily backpack
The best-designed backpack I have come across for my daily needs, living in Silicon Valley and working in the IT industry as a system administrator, is the Targus 17 City Gear Backpack. Very high quality, rugged, durable, there is simply no other pack as useful or reliable. The layout is superb, it's got a slew of functional, appropriate pockets and places to secure and store the different types of items you typically need to have handy: cell phone, pens and pencils, nuts and bolts, tools, water bottle, books, cables, chargers, laptop, tablet. The pocket for the tablet is lined with soft padding. The pockets for the cell phone and laptop have a velcro strap to keep them snug and prevent them from bouncing around. The laptop pocket has padded sides, so you can basically toss your laptop in there without worrying about it slamming around. It's got three large middle compartments. The first one has a pocket made out of a webbing material - I use this to keep personal hygiene items: toothpaste, mouthwash, ibuprofen, etc. I use the middle compartment for books, cables, CDs and DVDs which I keep within their own case. In the last compartment I keep both my personal and work laptops. The outer water-bottle pocket is perfect for a Nalgene bottle or for my no-spill coffee mug from Peet's Coffee (which is an excellent item in and of itself, by the way.) I also keep my Leatherman Blast tool in this pocket, there's enough room to put my bottle on top of it. I keep chargers, iphone cables, pens and pencils, all-in-one card reader and dongle in the pocket that has the cell phone pouch (yes it's big enough to hold all that plus cellphone. It evens has a headphone cable exit port.). Also in this pocket I keep my USB sticks which dangle from a convient hook. The outdoor material of the pack already seems fairly resistent to light rainfall, but if you need to make it more resistent you can treat it with a water-resistant spray or even purchase a raincover. (It almost never rains here in Silicon Valley so there's no need for me to carry a raincover.) The backpack even has an outer pocket area for holding a bicycle helmet and although I am not a cyclist, I can see it being highly useful for someone doing the bicycle commute. I've even been known to throw a small keyboard (of the musical variety) into the helmet pocket.
What can I say? This is an amazing backpack. A little pricey but well worth it. I believe I paid $65 for mine. According to the website, there is the CityGear 16" Commuter, 17" CityGear and 16" CityGear, all of which seem to be approximately the same design.