Singapore is small. So, 4-5 days will be more than enough for you to visit all there is to see. Make sure to take the night safari (not a real safari, and nothing comparable to what you can see in Kenya, Tanzania or South Africa), but it's worth it, because the night theme is unique. Also, visit trendy places like Clarke Quay. The shopping is to die for: Raffles City Mall will take all your money if you care to just stop there for 1 hour. The Marina Bay Sands hotel, which has the shape of a boat standing on 3 pillars is a "MUST SEE". Also, the Singapore Wheel is good: it's like the London Flyer, but with no queues ever! Imagine that! You can indulge in a foot massage, but in my book they can't beat the Chinese or Thai foot massages.
Since it's a small place, everywhere is nearby: a cab ride to anywhere will cost you between $6 to $12 (S'pore dollars). But the metro system is also very efficient and very cheap.
We went in December and really liked it. Apparently, it was supposed to be the rainy season, but it hardly rained while we were there.
If you'll be there for a while, it's worth dashing into Malaysia (tickets are cheap: about $200 roundtrip) and the flight is less than 2 hrs.

Please avoid the food hawkers who appeared to be over friendly especially in Newton Food court. The foods are yummy but we got ripped off! There's a very good foodcourt in Sommerset St however that served an array of really good foods at a very affordable price; it's called Food Republic. You may also want to visit the Apolo Banana Leaf in Little India. They serve really delish authentic Indian Foods. Just hop in the taxi and drivers know exactly where to take you. Safe trips!

One of the few beaches we have, the east coast is a nice place to come to at night for a cycle or a skate. There are no annoying pedestrians who get in your way. The quiet of the night lets you de-stress and you are left with your thoughts. Stop at the breakwaters and watch the sea bugs scurry about the rocks; after a while even the murky water looks tempting to jump into!

nice place to go cycling in singapore since it is the longest stretch of beach there but the water is polluted because of all the ships coming in and it is formed from reclaimed land so you don't really get to see many of the usual marine organisms you see in an intertidal shore. Nevertheless, nice place to go cycling but it is insanely crowded on weekends

i really love Singapore and really miss her too, she is a lovely country full of fun and adventures and the foods are amazing and the night life is exciting and interesting, even more awesome if you know people there :)
I want to travel there now, thinking about it now....