I've been thinking about this one for a while, with half an eye to coding it up: Mousehole or some other lightweight proxy with a list of sites. When you go to

I've been thinking about this one for a while, with half an eye to coding it up: Mousehole or some other lightweight proxy with a list of sites. When you go to one of those sites, it redirects you to your "to-do" list; google notebook or rememberTheMilk or something with similar capabilities. There's a button to continue to your intended site, but you've got the reminders right there of what you really intended to do instead of spending time on a site you have marked as a time waster. Could have priority markings and due dates integrated if it were a customized task list instead of google or RTM, and pop up the interstitial less often or less obtrusively when there's no important deadlines approaching, etc.