Fred is mentioning Kayak as his main search choice whenever it comes to looking for travel options. Just so you know there's also Mobissimo - an European venture funded by three VC houses: Cambrian Ventures, Index Ventures, and Benhamou Global Ventures. 

Unfortunately neither is relevant for the deals involving Romania - one gets quite expensive fares and (some of) the budget airlines such as Blue Air, SkyEurope or Jet2 (last two tie Central Eastern Europe with Western Europe quite well) are not included in the Romania-related searches. Not even Cimber Air is not in their list. Actually some weeks ago I wrote to the Mobissimo guys to include the few budget airlines operating throughout Romania and Central Eastern Europe but got no sign from them. Nor the airlines were included into the databases. I get so frustrated sometimes that Romania is not part of the game in this entire globalization process that's happening nowadays, I am sure it's just a matter of when and not of if. But the actual situation doesn't really make me happy. 

Anyways, it may be that Romania is not part of their plans or could be an operational inefficiency on their side as well.