If it gets too hot, SIN has a nice aquarium on Sentosa Island. The shark tube is the coldest spot in Singapore.

The Food Court in the high rise next door has some really good food at a reasonable price. Also some good Indian restaurants in the local area or you could wander over to Chinatown or Little India for food and shopping. If you don't mind a taxi ride, you can wander over to East Coast Seafood Park and have some Pepper Crab or some Chili Crab.

If you aren't that adventurous there are numerous restaurants on your side of the river and on the opposite side of the river.

Singapore also has an excellent zoo, if you are looking for something pedestrian. The night safari at the zoo is really good, but you are really cutting into your sleep time if you do that.

The largest bookstore in SE Asia is in SIN. Kinokuniya. There is also a large Borders bookstore down on Orchard.

SIN is a very nice, clean and perhaps a little sterile town but its a great layover. I wish they would change it back to the old arrival and departure time, the westbound flight is a b**ch.

There are also numerous WW2 tours available as well as Harbor Cruises

If you want to know about the less mundane things to do, you'll have to ask somewhere else. I don't post that kind of stuff in here...