there's many things to do in singapore! night safari, sentosa, shopping, all is pretty easy to get around by the MRT as well..... others have had similar questions answered really well in questions here: http://travellr.com/locations/5294/map-of-singapore about 10 years ago
While it's easier to give suggestion if your preferances are know here are a few general things to do In Singapore .
I won't repeat what's already been suggested by Josh
There are some awesome black pepper crab resturants at the east coast that you can try, also there is a great dim sum resturant on the Top foor of Paragon shopping center.
If you want to go shopping Takashimaya has been completely refurbished and had some cool deals.
River Quay has some new bars and resturants to check out as well. about 10 years ago