I blogged about this earlier and figured I'd post it here too. It works in Chrome and Firefox. Haven't looked too deeply at it working in other browsers just yet as it was just something I knocked up ad-hoc.
Anyway, create a new bookmark in your browser, give it whatever name you want and for the URL, use the code at the bottom. Now, whenever you click the bookmark, the current page your on will turn into a QR code which you can then read via your smartphone. Much easier to get sites on to your phone now without addons/extensions :) You can getback to the page by refreshing the browser (not clicking back).
Note: Google search results page don't seem to work, but that's because of Google's Chart API. Every other site I've tested works fine.