List of Discount Airlines and the routes they fly to from Venice
Ryanair (http://ryanair.com): This airlines gives you very good discount deals to a lot of European cities from Venice. The flights are all out of the Treviso airport which is easily accesible by bus from Piazzale Roma. Make sure you book flights well in advance (2 months at the least) because that's when you can get the maximum value out of the deals.
Easyjet(http://easyjet.com): Various locations (go see the website) and flights out of Marco Polo airport. The deals on this site are available until much closer to your flight dates (booking about a month to 2 weeks early would get you a decent deal).
Myair(http://myair.com): Flies to a lot of locations within Italy such as Palermo and Cagliari. Has good deals on international flights as well. However, most of their flights are during the week and hence might not be that useful.
Transavia(http://transavia.com): Offers discounted flights to and from Amsterdam. The only airline to do so.
Tuifly(http://tuifly.com): This airline offers cheap flights to various locations in Germany from Venice and back. Round-trip travel to cities like Berlin, Frankfurt for under 30 Euros.
Wizzair(http://wizzair.com/): Flights to easter europe. They fly out to Romania, Hungary and Bulgaria.
Vueling(http://www.vueling.com/?language=EN): Discount airfare to Spain. Fly to Barcelona, Madrid for dirt cheap rates.
Sky Europe(http://www.skyeurope.com/): Fly cheap to Prague, Vienna and Bratislava.
Go to this website http://skyscanner.net to search for deals on most cheap airlines. It is a flight search engine that searches for tickets available from most of these airlines.