One thing that I find that disadvantages travelers when they are traveling overseas is a lack of familiarity with their travel options. When you only use the large online travel agents you are likely to miss the smaller car rental companies, hotels, and airlines.
I live in Papua New Guinea and many of you who might wish to travel there would have previously missed on getting a great rate from Airlines PNG because a couple of years ago they were only known locally and did not have service agreements with the larger booking agents.
Find Budget Airlines
This is where WhichBudget (www.whichbudget.com) comes in handy. I especially recommend you use it for travel to/from/within Europe. Just type your departure city and your destination city and WhichBudget will tell you what budget airlines service those city pairs.
Remember you may need to play around a little with your city pairs to get a great price on a budget airline. Change your date and city pairs to see if you can find a bargain.
Another site that makes it easy to play around with city pairs is flychepo. Flychepo prompts you to select your arrival city. It will then tell you what cities have budget airlines that fly to your selected destination.