#linuxnus at irc.freenode.net has been around for quite a while.
We have some very interesting personalities Topics are not
restricted to FOSS. Feel free to drop in even though you are not
from NUS 
In addition, we also have #ubuntu-sg and #ntuoss
PS. Help in connecting to IRC can be found at:
Connecting to IRC - Linux & Open Source @
NUS
Do post in this list if I missed out any channels
You can also connect quickly via your browser using Mibbit.com - Easy and fast Webchat