Flattr.com is about to relaunch with something like that. You set an allotment for the month, then Flattr sites using their extension, and at the end of the mon

Flattr.com is about to relaunch with something like that. You set an allotment for the month, then Flattr sites using their extension, and at the end of the month, they get the share of your allotment, based on how much you visited them. I've already signed up both our sites, just waiting for them to relaunch.