I am not getting paid for this endorsement, but I needed to book some intra-Europe plane tickets yesterday, and found these sites. It made the process 100 times easier.
This site is excellent:http://www.dohop.com/
And so is this:http://wikitravel.org/en/Discount_airlines_in_Europe
Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.