Some website that allows you to do free SMS across the India I have collected some of the websites name but the condition is you have to Register you Email/Mobile number on site. Any way its free sms service provided by websites is cool.
Send free SMS anywhere in India
Way2sms now offers free mail service. get yourname@ way2sms.com
Email alerts on mobile. Its free.
Get SMS alerts on your mobile phone as and when the new mail arrives.
You'll receive only alerts for the emails you want, when you want them.
Notify recipients on their mobile while sending an email.
Access Yahoo and Gmail accounts right inside way2sms.
Get instant free mail alerts on mobile for your Yahoo, Gmail accounts

Ø http://www.indyarocks.com/mvas/sms.php
Entertainment & Free SMS Social Network.

Ø http://www.smsjunction.com/

Send Bulk SMS India. Free SMS, Group SMS, Group sms, sms India, SMS India, free SMS messaging, short text message, free, mobile, text messages. Free SMS India. Send Free SMS in India. Bulk SMS messages India, Group SMS India, Bulk SMS, SMS in India, SMS India Free. SMS any mobile phone in India, SMS Flirt in India and SMS Friends or join a SMS club.

Ø http://www.krify.com/cell/

What is Krify sms ?
Sending Free and Instant Short Messages to the Cell phones in India from any where in the world. We are poviding a web based interface by which one can send Free sms to India, for all the supported mobile networks, absolutely FREE of cost. We are the pioneer, First web based Free sms service provider in India.
How to send sms ?
Sending Free sms to india, is Easy. No Signup ! Nothing !
Just fill up the Cell Messaging Box shown above, select friends mobile number and your name, your email id and your message. Click "SendSMS"

Ø http://www.smsgupshup.com/signup

         SMS GupShup is a social messaging service to share and connect with friends and fans

Ø http://isms.ibibo.com/

Free SMS: SMS messages, SMS jokes, SMS shayari, SMS quotations, friendship SMS, love SMS, bulk SMS, group SMS, unlimited SMS on special occasions, share and forward interesting SMS messages for free using Free SMS Service

Ø http://messenger.rediff.com/

Rediff Bol allows to add friends with their rediff email id or with India mobile number. You can send upto 3 (three) only ONE free SMS to a specific Mobile Number without getting a reply. As soon as you send an SMS to your friend he/she will get an SMS request. Your friend needs to needs to accept that request for you to interact on SMS OR ask your friend to send GET as an SMS to 57333. The SMS message is limited to a maximum of 141 117 characters. You can also save your SMS messages in your computer as a text file. This is a reliable service I personally used many times. You can always send 1 more free messages per day to a number, if your friend do not respond.

Privacy: You can block a Rediff user from sending you SMS from Rediff Bol to your mobile phone. All you need to do is send BLOCK <user> to 57333

Example: BLOCK RediffUser

Charges: You will not be charged any money when you send SMS to mobile phones via the Rediff Bol. When your friend sends a reply, he/she will be charged according to the standard SMS rates by their mobile operators.

Rediff BOL supports the following GSM operators as of writing this article.

Aircel – Chennai

Airtel – Delhi, Kolkata, Chennai, Karnataka, Andhra Pradesh, Mahrashtra & Goa, Mumbai, Madhya Pradesh, Tamil Nadu, Kerala, Gujarat

BPL – Mumbai, Maharashtra & Goa, Tamil Nadu, Kerala

BSNL – Uttar Pradesh(W), Rajasthan, Haryana, Punjab, Himachal Pradesh, J&K, Maharashtra, Goa, Madhya Pradesh, Gujarat, Bihar, Andaman Nicobar, Kolkata, West Bengal, Assam, North East, Orissa, Andhra Pradesh, Tamil Nadu, Chennai, Kerala, Karnataka

Hutch – Delhi, Haryana, Mumbai (Orange), Gujarat, rajasthan, Kolkata, Uttar Pradesh(E), Uttar Pradesh(W), West Bengal, Chennai, Andhra Pradesh, Karnataka, Punjab

Idea – Maharashtra, Gujarat, Goa, Haryana, Uttar Pradesh (W), Kerala, Madhya Pradesh, Andhra Pradesh

MTNL – Mumbai

Reliance (CDMA) – All India

Reliance (GSM) – Himachal Pradesh, Madhya Pradesh, West Bengal, Bihar, Orissa, North East, Assam

Spice – Karnataka

Ø  http://india2sms.com/send.php

Send Unlimited SMS

At India2sms you are allowed to Send Unlimited Number of SMS's to your loved ones without paying us, Which means the SERVICE IS FREE TO USE.

No waiting Time

Our website assures you that you don't have to wait for a minute before sending the next message, so that you can stay connected !!.

Full Privacy

Your Personal information will never be shared with any Third Party , that is our assurance !!

SMS BLOCK SERVICE (Introduced)

Since our Website cares alot of its Users , therefore we are introducing a BLOCK feature in which , if u dosen't wish to receive SMS from our website or receiving some UNKNOWN messages, then you can USE this Service to Block your Number from receiving any Messages.