Here's a clever DIY project that solves a need, looks sharp, and can be completed in under 30 minutes with just a few tools. It's a leather frame strap, designed to attach a six pack to your bike's top tube for easy transport. The project is simple: take two belts, cut them to length, punch some new holes, and attach.
Of course, you'll want to be careful here; a pre-chilled six-pack could condensate and sacrifice the integrity of the cardboard. And, of course, the requisite - no drinking and biking.
But, the idea is solid, and works well for all sorts of things. See?
See the full how-to at Instructables. And be sure to check the comments section for more tips: 6-Pack Beer Holder for Bicycle