Hmmm. At least since about 2wks ago up to now...
And what I do on a given day varies greatly, though here's random stuff I do frequently over a given week (in no particular order):
~classes (mostly Computer Science)
~exercise w/ buddy
~"study" (anything class or science related; having recently done a group study session, I've found what I consider studying is merely thinking deeply about the topic at hand)
~read science news, technical news, nonfiction books, xkcd, etc.
~think (about either science, philosophy, my future, or awesome stuff that would never happen but is cool to think about anyway)
~attend (what will hopefully turn out to be) interesting events on campus
~watch Firefly or SouthPark episodes online