I'm putting in another vote for Osprey as well, in this case an Escapist 32. I ordered it online from REI after reading an article from Bicycle Times. It has tons of room, and can be cinched down when you don't need all of it. I use it for everyday commuting, and on the weekends load it up full with gear (helmet, shoes, sunscreen, snacks, ect) for roadbiking trips. Just toss it in the van and everything is right there. It comes with a waterproof hi vis cover too.