I don't know if it's cycling specific but I use an Osprey Momentum 34 for commuting. It has a padded section for a laptop and plenty of storage. I only bring my laptop home if I'm going to be travelling as it's lighter than my home laptop. I don't have any problem carrying the laptop although normally I just bring an iPad back and forth. The Osprey comes with a lifetime warranty and I'd recommend it or an equivalent model (not sure if they still make the Momentum).