Wow! It's a great pleasure to hear that we have a MongoDB User Group in Sri Lanka. I just sent a request to join to MongoDB User Group page in facebook. I really worry about got so long time to join the community of MongoDB.
You can also join to Colombo MongoDB User Group from this link.
I really didn't know there are much more people in Sri Lanka, who is interested in MongoDB. I hope to join community and enjoy MongODB!!!