Googling the wiki page for that airport is a great way to find all its nonstop destinations.

Air Arabia (Sharjah)
Air-India Express (Chennai)
Air Italy (Verona)
Air Sahara [a.k.a Jet Lite] (Bangalore, Chennai, Delhi, Male)
Austrian Airlines (Vienna) - [Service starts October 2007]
Blue Panorama (Milan-Malpensa)
Cathay Pacific (Bangkok-Suvarnabhumi, Hong Kong, Singapore)
Condor Airlines (Frankfurt)
Edelweiss Air (Zurich)
Emirates (Dubai, Jakarta, Malé, Singapore)
Eurofly (Milan-Malpensa, Male)
First Choice Airways (London-Gatwick, Manchester)
Indian Airlines (Chennai)
Jet Airways (Chennai)
Kuwait Airways (Kuwait, Jakarta)
LTU International (Düsseldorf, Munich)
Malaysia Airlines (Kuala Lumpur, Male)
Martinair (Amsterdam)
Mihin Lanka (Bangkok-Suvarnabhumi, BuddhaGaya, Dubai, Male, Singapore, Tiruchirapalli, Trivandrum)
Qatar Airways (Doha)
Royal Jordanian (Amman)
Saudi Arabian Airlines (Dammam, Jeddah, Riyadh)
Singapore Airlines (Singapore)
SriLankan Airlines (Abu Dhabi, Bangalore, Bangkok-Suvarnabhumi, Channai, Coimbatore (Starting October 2007), Doha, Dubai, Delhi, Dammam, Goa, Frankfurt, London-Heathrow, Paris Charles de Gaulle, Karachi, Kuwait, Singapore, Hongkong, Tokya-Narita)
Thai Airways International (Bangkok-Suvarnabhumi)