We use various courier services depending upon the area.. Well to be precise now we have Bluedart mainly via eBay powership and we are more than happy with their services.
Regarding other areas, as we mentioned earlier, we use different courier services depending on the area, following information will be usefull to all:
TN & AP -- Professional
KN -- GMS
Rajasthan -- Pushpak (Rajasthan Exclusive)
Kerala -- Speed and Safe
Gujrat -- Maruti Services
Chattisgarh, Jharkand, Bihar -- Akashganga,
North East -- DTDC & First Flight
UP, Uttranchal -- Blazeflash and Overnight
J/K -- Akash Ganga
Haryana - Madhur Courier
Punjab - Blazeflash and Overnight
Of course these are for Tier II and Tier III cities. For Tier one you can use basically any courier..
Hope this information helps!!