Use HSBCFLY as makemytrip coupon to get 7% cashback on domestic airfares, 5% cashback on international airfares and 10% cashback on international hotels. However, you can get this discount only if you use a HSBC credit card for booking of your flight or hotels on makemytrip. 
Makemytrip offers for Visa Cards – Valid till March 31, 2012

• Use Makemytrip promo code VISAMMTINT for International Business class flights
• Use Makemytrip promo code VISAMMTOBT for International Holiday
• Book 3 domestic tickets and get 1 ticket free – Use promo code VISAMMTDOM

If you are using ICICI net banking use the promotion code ICICINET to get following discountsRs 200 Cashback on domestic flights

• Hotel Bookings – 15% of base fare as cashback for domestic hotels
• Bus booking – 20% cashback
• International Flights – Rs 750 Cashback / Rs 1200 cashback (depending on flight duration)
• Rail – Rs 200 Hotel Voucher free with every booking

Update on Feb 27, 2011 – Use FLYFREE as makemytrip coupon to avail the ‘Buy 1 Get 1 Domestic Ticket Free‘ on makemytrip