which airways offer cheap ticket from Delhi/chennai and back?

you can search here in the travel column :

http://in.msn.com/

Just enter the details and you are done !!!!

You can fly to Manila, Philippines on Philippines airlines, then over-there buy the tickets to India (Air India, Singapore airlines etc.) and it will be much cheaper, and you will save money on taxes too. Instead of buying the entire trip from the U.S.A. Do your homework, check different sites like travelocity, etc. And check prices and specials sales on the airlines sites. Have fun, enjoy your trip.

Jet Air

Fares vay with departure days/dates/airlines.

Checkout Yatra search-booking engines which offer cheap fares.

I think the Daccan Airlines is the chipest one....