Anything and everything.
Pretty vague, yeah? Well, it could come from an lick I hear on the radio, or from an idea I stumble upon while doing something like taking out the trash. I could be at work and have to keep an idea in my head long enough to locate a piece of cardboard/paper/something to write on to assist me in transporting the idea to a location where I can flesh it out into something tangible. I could be inspired by listening to the latest release from any profilic artist, mainstream or underground, or simply from playing some video games, from the past to the present. Inspiration can strike at any moment, and it's up to you to be able to capture those moments via paper, recorder, or some other medium so you may be able to flesh out those ideas into pieces that inspire other people.
In a perfect world, obviously, inspiration would strike when it is most convenient. However, we don't live in a perfect world, and therefore, we must handle our inspiration the best we can, even if that means sacrificing an idea or two in order to live our lives.
But in my experience, enjoying life is what spurs my creativity. And sadly, that's advice I need to follow myself.