Street Directory used to be one of the best known site that provide online Singapore street directory, however it fell in 2008. After that, new and better alternative web sites rise and grab the street directory market share.
The neat and clean interface immediately brought to my attention. It is simple to use and the site responsiveness is excellent. The old Street Directory web site could take some time for an address query and filled with a lot intrusive advertisement.
There is also iPhone app selling for USD2.99.