I have mentioned Airpaz above (been recommended by one Indo friend of mine), but recently I had a very unpleasant experience with them, resulting in money & time loss (and could have been much worse if I didn't check my spam folder). Basically I made a booking, approved payment with 3D Secure, booking got confirmed, I got PNR, made a printout and thought I am all good. Yet, I did not see a letter from Airpaz, which I wanted to forward to TripIt in order not to input data manually. Checked spam folder, and to my utter surprise saw the e-mail informing me about my reservation being cancelled (!). Had to rebook with another agency, and by that time ticket price increased. To make things worse, Airpaz charged my card (not just made a hold) and processed refund as a separate transaction, so I lost money also on currency conversion (thanks to Citi, they agreed to compensate me the difference).
Won't be using Airpaz ever again and do not advise to use them.