My mind is filled up with useful and (moreso) useless facts and knowledge, because I absolutely love accumulating interesting information. I will jump at any chance to go to a pub quiz and have had friends call me up to ask obscure questions from "How long ago did Arwen and Aragorn get together before the start of Lord of the Rings" to "Can you explain this whole Higgs boson thing to me?".
I do a ton of reading. Lately I've been reading lots of world history books and political science stuff. I'll often take a break from the nonfiction and read some scifi or historical fiction as well. And I'm a big comic geek so I pick up the new issues of my favourite series each week.
I also love podcasts. Skeptic's Guide to the Universe, Quirks and Quarks, Slate Political Gabfest, Hardcore History, Astronomycast and History of Rome Podcast are my favourites. My absolute favourite tv show of all time is QI, but some other favourites include Peep Show, Always Sunny, Doctor Who, and Any documentary with David Attenborough.