I use an old REI day pack that isn't made anymore. Every once in a while I look at replacements becasue it isn't going to last forever. I like it becasue it has 2 water bottle pockets on the sides, and another small storage pocket on the back, so you don't need to dig thru the body of the pack to get to them. I also like that they totally zip shut -- nothing will ever fall out of em.
2,000 miler