Biking is more effcient than walking, based on distance to calorie.
since everyone else had great responses to the paper question i'll start out with the backpack one. Ogio makes a couple great packs, i really enjoy mine. It's an Ogio Atrix, their entry-level pack, in Hi-Viz Orange. I was worried it would be too small, but I haven't had a problem going to and from school, as well as some grocery shopping trips.
If you want a messenger bag the good ones are over $100. Chrome, Timbuk2, and many others make great ones, but like i said they'll cost ya. Go large with a messenger bag, i have a small Timbuk2 one that i got off CL for cheap, and it sucks only based on the size. Another downside is you can't fit a waterbottle on the outside of it, which i like to do since my Nalgene doesn't fit in the waterbottle cage. I also like an outside pocket for coffee.