Dear Mr. Gopal,
I would disagree with Mr. Rahul. The sitting fee paid to Independent Directors shall be liable to service tax. Fee paid to executive directors shall not be liable to service tax, since they're generally in the employment of the company.
As per the definition of service, service does not include the service rendered by employees in the course of their employment. Independent Directors are not the employees of the company.
Further, sitting fee paid to independent director is neither there in the Negative List, nor present in the Mega Exemption Notificaiton No. 25/2012.
Hence, according to me, such sitting fee paid to independent directors is liable to service tax.
Others may please offer their comments if they disagree.