I'm looking for any suggestions you might have for a good commuting backpack. My ride to work is only about 2 1/2 miles each way, but I prefer to ride in my cycling clothing rather than my work duds. I also carry a laptop, external hard drive, power cords for each, and a mouse. I also work out over lunch so I have my running clothes, running shoes, and iPod. Plus my cell phone, wallet, and keys. So basically, I need a bag that's big enough to carry 2 pairs of shoes, work clothes, running clothes, the computer equipment listed above, and my lunch. Comfortably, if possible. Any suggestions?