Hi,
Well the obvious answer is "Japan", but assuming thats not an option, try these ...
1. Japanese Cultural Society (JCS) on Middle Road. Very inexpensive and quite well organised.
2. Berlitz at Orchard Road. Expensive and focussed on conversation rather than written/grammar skills.
3. Bunka at Cecil St or Orchard Road.
4. Pyaess at Sinsov building.
There are loads more. Just Google search for them.
Good luck / ganbatte.
i've tried bunka. to me, learning the basics there are quite ok.. but my advice if you are intending to do JLPT exams, you should go to ikoma language school, at shaw house beside lido. ikoma is more coherent to the exam syllabus. =)
This is for more advanced students so just treat it as infomation. Here are the web links; http://www.beelinetv.com - television in various languages from around the world - best link for Japanese is the The Fuji news network.
If at some time in the future you aim to do some serious reading then try this;
http://www.rikai.com - clever website in both Japanese and English and able to translate from one language to the other ( I am using the word translate very loosely here).