I tried out Pomodoro, a tomato-like application that is basically a timer for your computer desktop. It times work sessions in 25-minute increments (you can adjust to 30 or 35 too), then gives you a five-minute break. Today, in an 8-hour day on campus (8-4), I did 8 25-minute sessions and finished grading a set of compositions, finished reading a book ms. and writing a report on it, read over a chapter in a grammar book for class tomorrow, and read over part of a tenure file. Off the pomodoro clock, I also met with three students and had lunch with the Department chair, where we discussed some business. So I pretty much did a full day's work, without working on any of my own research! (That's great except for the last part.) I did some blog posts and surfed the web a bit, but otherwise was disciplined enough for a day I don't teach. I've cleared my desk of all but teaching and research tasks.
Pomodoro also keeps track of your work sessions. You can create different labels for tasks and chart your work like that. If you don't need productivity tools like that, by all means don't bother. I could do without it, but I find it fun to try. Any change can be motivating, so I can imagine that NOT using it after a while might be a good change as well.