RoamTheWorldCellPhones.com

Cellphone GSM Frequencies: 900/1800

(This means you will need a GSM cellphone that will work on 900MHz or 1800Mhz to use it in India.)

Cellular carriers for India

Aditya Birla Telecom Limited (IDEA Cellular BEHAR)

Frequency: GSM 900/1800
Website: www.ideacellular.com

Coverage Map (NONE)

Aircel Cellular Ltd.

Frequency: GSM 900/1800
Website: www.aircel.co.in

Coverage Map (NONE)

Bharat Sanchar Nigam Limited (CellOne All India except Delhi & Mumbai)

Frequency: GSM 900
Website: www.bsnl.co.in

Coverage Map

Bharti Airtel Limited (AIRTEL)

Frequency: GSM 900/1800
Website: www.airtel.in

Coverage Map (NONE)

Loop Mobile (India) Limited (Loop Mobile)

Frequency: GSM 900
Website: www.loopmobile.in

Coverage Map (NONE)

Mahanagar Telephone Nigam Ltd (Mahanagar Telephone Nigam - Delhi) (MTNL)

Frequency: GSM 900
Website: http://mtnldelhi.in/

Coverage Map (NONE)

Reliance Telecom Ltd (RELIANCE TELECOM LIMITED - Madhya Pradesh)

Frequency: GSM 900/1800
Website: www.rcom.co.in

Coverage Map (NONE)

Tata Teleservices Ltd

Frequency: GSM 1800
Website: www.tataindicom.com

Coverage Map (NONE)

Vodafone Essar Cellular Limited

Frequency: GSM 900/1800
Website: www.vodafone.in

Coverage Map (NONE)

If you've used either of these networks or roamed in India, please post about your experience and the cost. Feel free to ask questions.