eBags makes some great backpacks. I've been using one of their bags for about 4 years now and it's held up very well. I can't remember the model of bag I have.
I use one of those drawstring type bags, but designed for a laptop (so has a cushy spot for the laptop). Smaller, can fit easily on planes/any type of travel, etc. Love it.
If you are going to be walking a lot though, you need to add padding to the shoulder area.