[torial]

To that end, a great free tool that I've been using is called Workrave: http://www.workrave.org/welcome/

Otherwise, I don't get off my butt much -- but this reminds me. And it is highly configurable.

[kungfooey]

I second the recommendation of Workrave. It's easily configurable and it works quite well to remind one to get p every now and then (or at least to look away from the monitor for a few seconds).

[silentbicycle]

xwrits (http://www.lcdf.org/xwrits/) is good, too.