Effectively, you allocate a portion of funds every month to Flattr. Over that month you can click the "flattr" button on any site that has one, and at the end of the month your monthly contribution is split evenly among all of your "flatter" choices. I don't know if they added recurring donations, last I looked at this service was a couple of years ago.
EDIT: Apparently they've made it an extension that tracks your browsing history. That's just ridiculous. It's also a shame -- Peter Sunde used to be quite pro-privacy. But they _did_ say they wanted to liberate the extension.
