I first became aware of Buster Mcleod from his All Consuming project. He has a lot of projects that seem to spiral off from what he was doing with All Consuming. Projects that track a particular time of day on Flickr. Projects that display what is in season for your location. His Morale-O-Meter used to track his mood and other statuses throughout the week. He sums it up in his post "History of my self-tracking":
The reason I am obsessed with self-tracking is because I think there is a way to track yourself in such a way that it leads to epiphanies about yourself, about the cause and effect of things, in such a way that these numbers would eventually be able to tell you things about yourself that you didn’t already know. This is the only reason to self-track, in my opinion.