I recently discovered Alite Designs (who produce and sell a variety of outdoor-ready products), but their Bike to Beach bag is the one I'm most excited about.
Made in San Francisco, the bag easily coverts from tote to backpack (and not in the ugly, clumsy with too-many-moving-parts way I've seen from other manufacturers). It comes in a few different colorways of 18oz canvas, features a U-lock pocket, and the adjustable leather straps making this a highly versatile tote.
For $135, this bag is an timeless classic that will last you years and years to come (not to mention Alite's lifetime guarantee!)
Check it out over in the Alite Designs shop
They also make a smaller version here!
Photos courtesy of Alite Designs.