I've got my 6-year old Windows desktop sitting here that I rarely use for anything anymore, so it mostly just acts as a print server, file storage, Zumocast server, and now a Bitcoin miner with low priority.  As it's ancient, I only get 700 khash/s, but I'm not paying for the electricity so it's essentially free money.

I've also got my laptop here that I use for work/play, and I'll switch on a GPU or CPU miner if I'm not doing anything with it at the moment, but only one thread so I don't prematurely cook the CPU to death.  In all honesty with the latest difficulty change, I'm probably going to stop mining on the laptop entirely once I get my next payout. 

Your phone is 1/2 the hash rate of one computer I routinely use. That's both amazing (for you) and sad (for me).