airtel 110 balance on 100 recharge via airtel money is a good offer.
You can also avail 110/220 balance on 100/200 without registering airtel money , recharge via m.airtel.in (mobile site)
i stopped using airtel money, no good offers now, they had good offers like 50 % cash back on bookmyshow.com (cap 200rs) 25% for second tranx