J/FIT stability balls, for sitting-on - I tried a TKO, but it had a persistent smell that made me nauseous. I can't say yet that I use mine for hours at a time, but it's fun to bounce on now and then, and costs $25 at Amazon. I'm 5'11" and need a 75cm ball to balance properly.
I have often benefited from recommendations for Things I Didn't Know I Wanted.
Given that Less Wrong is a community of unusually intelligent, critical, and self-improvement-focused people, I suspect we can generate a pretty helpful thread of product recommendations — perhaps even a monthly thread of product recommendations.
Rules: