Use eBuddy for Free on Airtel to chat on Gtalk, yahoo etc.
First create a new GPRS settings profile with the following parameters:
Proxy: 74.3.160.66
Port: 80
APN: airtelgprs.com
Now open eBuddy, enter the following in Front Query:
wap.mauj.com/cgi-bin/nph-get.cgi/000100A/http/