I use stickk.com. I decide a time period over which I'm not going to use the net (typically, between starting work and 4pm, for an entire week); I then pay out

I use stickk.com. I decide a time period over which I'm not going to use the net (typically, between starting work and 4pm, for an entire week); I then pay out $20 to an anti-charity of my choice if I fail. Works a charm.