I use a hosts file of ad site domains aliased to localhost. A web server on my machine redirects the default page at localhost to my to-do list on http://rememberthemilk.com . In addition, I use OpenDNS to block distracting sites, and redirect block.opendns.com to localhost, which is then redirected to my to-do list.
This is brilliant.
We could ask, "why not exercise self-control?" Some say there is no such thing as will power. Some insist otherwise. We could embark on a course of meditation, and this may quiet the chatter in our own minds. But it will not address the chatter of the Internet, which replicates the internal chatter of the mind (or at least my mind). Must we assume the burden of spiritual equipoise entirely from within?
The chatter of the Internet is not only distracting for us: our machines expend energy and clock cycles to provide us with extraneous cognitive load. The low signal-to-noise ratio costs them as well.
The domain name filtering service OpenDNS displays a block page at http://block.opendns.com if a site meets the criteria for filtering. This is negative reinforcement. We might provide positive reinforcement if we were to substitute an online to-do list, such as http://rememberthemilk.com, for the block page should we lose focus--to mention a crude first step.
RescueTime looked like a great idea, but for me, it became another example of mechanized negative reinforcement. It's too easy to defeat and ignore. There should be more of a feedback loop with users to provide them with real-time positive reinforcement. It's not enough to reply that a tool is only useful in the right hands. Some attempt has to be made to understand how to develop the right habits or the hands will vote with their feet.