I bought this one not too long ago in large ...

wiggle.com | Osprey Radial 26 | Backpacks

It's petty nice, especially the frame that keeps it directly off of your back.

I carry an assortment of tools, a reflective jacket / windbreaker, a change of clothes, 2 tubes, small chain lock, small pump, bottle of water, and a small laptop.

I wish it were bigger sometimes, there's also a 34 version.