I used to visit Singapore quite often in the late 90's. As was mentioned, it's a small place with a lot of traffic. There are a large number of very modern, tall commercial buildings, if you are into geometric shapes and the like; beautiful, colorful skyline at night. Some remnants of colonial times (like Raffles) remain, but not many. There is an old section with traditional shops like the butcher shops where most things are alive (turtles, etc.) and are killed for you; the Indian section is also quite colorful. As was also mentioned, the view out to sea is one of moored ships. Whenever I was there, the sun was very bright and when it rains, you have to take cover.
When I first went there, one of my business associates (a Singaporean) told me that were only two things to do there; shop and eat. That said, it's a terrific place to eat (everything and anything) and probably best for street shooting and the urban facades, at street level. People are very nice and the food (hawker) centres are not only good for eating, but are an interesting cultural (and visual) institution. If you like to explore food, you'll love Singapore.
There is a place called the Night Zoo, that is one of the stranger things that I have seen, although not so much for photography.
