Did you try Google? Most flights are returns, so if you look at flights from the Isle of Man, it will list all the destinations you can fly there from as well.
Belfast City - Citywing
Birmingham - Flybe
Bristol - easyJet
Dublin - Aer Lingus Regional
Geneva - Flybe
Glasgow - Citywing
Gloucester (M5)- Citywing
Liverpool - easyJet and Flybe
London City - British Airways
London Gatwick (North)- easyJet
Manchester (T3) - Flybe
Newcastle - Citywing
Stansted (to 26 March 2016) - Flybe