I'm really productive when I am alone. Hobbies help yes, but I think attitude is more important. I am a competitive person with personal goals so being completely alone just playing pool, online poker, reading, writing, exercise, etc. can take up so much time for me. I'm the only person at my college pool hall who plays more alone than with others. And I love it! I feel like a freak (in a good way) in this regard. I'm not even that good at pool.
If you're just doing something to just pass the time, it will get boring very easily. Find something that inspires you to at least Google "tips for __________". That's a good rule of thumb.
When I am truly 'down and out' lonely, I web-surf mindlessly. It gets pretty ugly because I have too many bookmarks and I am a habitually 20-tabber. It hits rock bottom with porn. This is what I don't want to do. It's really a self-loathing activity because I don't want to think anymore, when in fact, deep thought is probably my best gift.