I have a BIG laptop that I need to transport for work as well. My company got me a waterproof case (so I don't have to worry about riding in the rain):

http://www.amazon.com/SealLine-Compu.../dp/B000OV76UC

I have the large, and it (barely) fits inside my Novara Communter pannier, which I love:

http://www.rei.com/product/780448/no...single-pannier

Between that pannier and a smaller Arkel on the other side, I can get laptop, towel, clothes, lunch, etc. with no problem.

I should add that once I forgot to lock the clips on the pannier, and it came off and rolled down a busy street with my laptop in it. Awesome! Fortunately, between the padding on the Sealline case and whatever else was in the bag, the laptop was fine.

Dave