Airtel has recently launched an attractive offer of Mobile Internet at Rs. 99. Well worth it for non-Blackberry users like me (I use the Nokia E63) who do not have a standardised rate plan for mobile internet.
There is a 2 GB monthly cap, but given the slow speed of GPRS/ Edge connections, it is unlikely that you will ever download that much in a month :)
An interesting tidbit - when I called Airtel to activate this plan, I was told through the IVRS system that if I want to talk to a customer service representative, I would be charged at the rate of 50 paise per 3 minutes.
Of course, calls to customer service abroad are always metered and in India, many service providers like Tata Sky and Tata Indicom Broadband do not provide a toll free number. In principle, I am fine with paying for quick resolution through phone, but in that case, I do not want to hang on to the line and keep pressing buttons. Give me a dedicated number and guarantee a resolution under 3 minutes and I will gladly pay.