Watch Trailer Park Boys on YouTube, listen to music, read about politics, draw, take long lunches, besides stuff like what you listed. Sometimes there's only so much you can do while keeping productive, especially if your employer hasn't planned your time well enough.
More specific to my current situation, I am looking into applying for grants to visit CS conferences, gearing up to write a paper to submit to a conference (that's going to take some time), and applying for a graduate certificate program at MO Science & Technical (formerly MU Raleigh of Three Guys fame... sorry gotta plug my home state ;) Hopefully I may get my employer to pay for these in part, or get benefits of some other kind.
I'm not sure about other programs, but Raleigh offers an online 4-course program (graduate level) and at the end of which you get a certificate from them. If you get a B average or above you are automatically accepted into the graduate program (no GRE). Also, there are always various other forms of certification which you may be able to cajole your employer into helping you pursue.