Ryanair

The cheapest way to fly in Europe but be warned:

1. It will drop you at the most inconveniently located airports so plan ahead of time how you're actually going to get to the city you thought you were going to.
2. bring earplugs or a good playlist unless you want to listen to them advertise scratch cards and smokeless cigarettes every five minutes
3. bring a sleeping mask/blindfold if you'd like to stand a chance of sleeping because the seats really are as bright as they look folks.

http://www.ryanair.com/en

http://www.skyscanner.it/  - a great fight/price comparison website