I think Flattr is the most promising way forward as a source of non-ad revenue for websites as it doesn't require explicit user interactions once set up, it jus

I think Flattr is the most promising way forward as a source of non-ad revenue for websites as it doesn't require explicit user interactions once set up, it just runs in the background, tracks what you consume, and then automagically distributes your allocated funds to the sites in accordance with your consumption.