Thank You!
I'm wrapping up my day in SIN now. Based on the ideas here, I took the free shuttle into the city from the Terminal 2 Singapore Visitors Center and wandered there for the day. Lots of reasonable places to eat and shop there... with friendly free shuttle service right from the visitors center desk.
The "tour guide" on the free shuttle is great too, pointing out points of interest, describing everything we passed, and taking questions from the tourists on the bus.
What a great way to spend a layover... without spending any money!