Originally Posted by
whoiswes
I run a REI Flash for my 10 mile commute -
http://www.rei.com/product/778466/rei-flash-18-pack
It's super light, packs down to nothing when I don't need it, and has plenty of room for my change of clothes/lunch/netbook. Also is hydration system compatible. My wife and I also use it as a daypack when hiking/backpacking.
I used to use a larger backpack (also REI) and more recently two different Timbuk2 messenger bags - the Flash beats them all in versatility and comfort. Best of all it's only $30 (and cheaper if it's on sale or you have a dividend to spend!).
My gf has one of those, and I find the L L Bean Stowaway more comfortable and easier to use with the external pockets. Plus, it's got retroreflective parts for the night commute. They're both good packs, both the same price, almost the same size, and just about right for my regular commute.
I also have used the Kelty Shrike both on and off the bike, and it's the most comfortable pack I've ever worn. Especially when carrying heavier loads.