Azuon is a subscription-based service dedicated to helping you find budget flights (there are a variety of price options, but a recurring annual subscription costs a little over $18, for instance).
As we write, the program supports the following low cost airlines, with more being added all the time: Aer Lingus, Air Berlin, AirAsia, airBaltic, blu-express, Blue Air, easyJet, Germanwings, Iceland Express, jet4you, Pegasus, NIKI, norwegian, Ryanair, SkyExpress, smartwings, SpringAirlines, SunExpress, Tiger Airways, transavia, TUIfly, Vueling, WOW air, Wizz Air, Wizz Xclusive, Air Arabia, Air One, Thomson, Volotea, Monarch, Jet2.com, eurolot.
Normally this kind of tool would be a web service only, but Azuon provides so many options that a Windows client makes it more usable. You'll only be able to use the program in demo mode, until the subscription is paid (airline names and departure dates are mostly hidden, there are a few other snags), but that's still enough to get a feel for how it works.
Why should you pay at all, though? Azuon says one key answer is its ability to search flight combinations between low cost airlines to give you the best possible deal. So not only can they locate the cheapest direct Malta - Riga flight, say, but by allowing for multileg trips (Malta - Oslo - Riga) there are sometimes spectacular savings to be made. And ones you won't easily find in any other way.
You also get a great deal of control over your trip. You're able to decide exactly which airports you'd like to use, say; the minimum and maximum time you'd like to spend at your destination; the minimum and maximum stopover time you'll accept on a multileg trip, the prices you'll accept (or not), multiple sets of date ranges when you might want to take these flights, and the list goes on.
And there are some unexpected tools to help you along the way. Select a particular flight, for instance, and you're able to view its price history. Is it looking cheap right now, or maybe postponing your trip for a month will save you a bundle? It's all included in this very comprehensive tool.