Found this in the underground going home from work

1. If your contract allows it (and it should), get more involved in public dev community. Your employer benefits greatly from making a small closed source core product, with a giant open source ecosystem around it. Write public articles. Working in a community larger than one single business is fun.

2. Start a company coding club, a "labs" division, work in a slightly more exotic language. Great if your employer gives you time, but using some of your own is worth it too. Work on non critical tools, creative experiments. Sometimes you stumble onto incredibly valuable ideas which would never have popped up if you had strictly followed stakeholder requirements.

3. Listen to your body. If you feel restless, go for a run. If you feel tired, take a nap. If you're stuck, wander around the company. If you feel down, go find a place with more than a dozen trees. And always have a notepad nearby for doodling!