For planning purposes, my team currently assumes 50% of my time will be spent actually working on tasks assigned to me (be it researching on StackOverflow, debugging, or actually typing code directly related to a task). The rest of my time is spent doing things like code reviews, helping others with particularly nasty tasks that are assigned to them, and even socializing with people (in the asker's words: playing pool, ping pong, chatting, etc). All of these things help us, as programmers, to do our actual jobs better.
Code reviews familiarize me with sections of code that I might not otherwise have reason to ever see. This pays off six months down the line when I'm writing code that might have a nasty interaction that I hadn't initially considered, and I can check to make sure.
Helping others helps the team in the short-term, by helping them get a task done earlier; but it also helps me in the long-term, by giving me a social lubricant ("leverage") in the future to get them to help me on my particularly nasty task.
Socializing helps you get to know other people -- what they're good at, what they like to do, what they dislike to do, etc, etc. While this might not seem directly useful, it can give you great insights in to how others think: what to look for the next time you're code reviewing (if they hate SQL, pay particularly close attention to the SQL they're changing!). It also help you know who might be a good resource to get help from (if you're working on a tricky bit of UI, go talk to the best UI guy you know). The most important thing is to make sure you're socializing with a broad set of folks -- don't just restrict yourself to your own team -- hang out with somebody from another team completely separate from yours, make friends with on of the IT guys (he might prioritize unlocking your AD account next time you've forgotten your password!), make friends with the marketing department (they might give you a heads up when they start thinking about promising a feature that isn't in the requirements), etc, etc.