Courier Bag

Those big-ass one-strap carry-alls that bike couriers use to ply their daily trade. Waterproof, built to last, large enough to sleep in. If you're looking to purchase one, the two critical metrics are, "Does it carry a case of 24 in bottles?" and "If those bottles all break, is the bag tough enough that the glass shards will not rip through the back and pierce my spine?" If the answer is yes, you've got the real deal. If not, you're being hoodwinked by some slick operator selling "urban cultcha" who should be avoided at all costs.

Timbuk2, a SF company full of nice, young, entrepreneurial lads, will make you up one special with the colours of your choice.

I enjoy my Timbuk2 bag, which is one of their DeeDog models, in my 1st racing team colors and an embroidered team emblem (Aurora Cycles, Seattle, WA). It can easily accomodate a medium sized dog. Or a bike helmet and floor pump.

Although many companies now make courier bags, of special note is Ortlieb, a German company. They make a series of bags for messengers. All their products are waterproof. Not just water-resistant, but waterproof to the "the-water-pressure-will-squash-you-like-a-grape-before-this-bag-will-leak" kind of waterproof.