The stems I get from breaking up weed to smoke, I just eat. I call them "scooby snacks." I eat the seeds, too. The stems I get from breaking out eighths to sell, I've been keeping those, I now have around half an ounce of them, and no idea what to do with them.
Back in the day I smoked stems when I couldn't find any bud, but that's not an issue any more.