I want to learn how to make a social game in facebook. How to go about it. I think you would need a team of devs. What languages are used to make social games like farmville, happy aquarium, etc.
Are any tuts available or any book?
There are both books and tutorials for this. Countless in fact. What you are trying to do is not trivial, hence the amount of books one could suggest.
Lets break your question apart:
I think you would need a team of devs.
There are really only two reasons for working in a group. First, more people can complete more work in less time. Second, having more people requires less knowledge of each single individual. But if you're asking that question I'm tempted to state that the answer is simply no; if you feel you can't judge the amount of work involved or are new to the subject I think you're not ready to work in a group. But it sounds harsh. Remember that working (effectively) in a group is hard.
What languages are used to make social games like farmville, happy aquarium, etc.
"Social games" are all the hype right now, but vaguely defined. But since you compare it to Farmville and the like I take it that you mean a web game. Those can be done in any language or platform that targets the web (surprise!). Flash, php, python take your pick. Social is also a broad term that's vaguely defined. Do you by social mean "Facebook integration"? How about MySpace? Or Twitter? Or why cant the game itself be social (whatever that means).
Since I'm strangely enough in a good mood right now, I have created a roadmap for you:
Farmville clone 101
You're in for a hell of a ride. 50% don't make it past step 1, 90% don't make it past step 2. This is hard.