I have an Osprey Stratos 18 which I use for cold weather mountain biking and nordic skiing. I'm amazed at how much lighter the load seems in this pack than in other "women's" packs. I also like Osprey because the packs come in sizes based on torso length.
And there's a great attachment point for my SPOT should there be unplanned adventures. 
The Stratos 18 is probably too small for what you want, but I bet one of the Osprey packs would work really well.
PS - I hate my TimBuk 2 messenger bags. They will not stay in place for me no matter what I or anyone else does to adjust them.
Last edited by SadieKate; 01-05-2009 at 10:19 AM.
Frends know gud humors when dey is hear it. ~ Da Crockydiles of ZZE.