If your plans are somewhat open-ended and perhaps you are willing to pick up or drop off a city or two on your destination list, I would suggest looking into the Eurail Pass. The pass will allow the given traveler a certain amount of travel dates in which you can use the many, cross country trains and even a few, select ferries out to Greece or southern Spain. The 15 day traveler pass allows you to travel as many times as possible within a 24-hour window in exchange for one day of travel. Most destinations are accessible in at least one to six hours. The 15 day, youth global Eurail Pass ran about $800 US dollars at the time of our purchase, but it was an amazingly easy and comfortable way to traverse all over Europe.
The second of your cheaper options would be to use the Ryan Air airline company operating strictly in the UK and European nations. You can visit the site here and book a flight to just about any overseas destination for as cheap as about €5. The only catch with Ryan Air travel is the bag limitations. If you are stealthy enough to pack light and small, you are allowed one carry-on for free. They charge for any checked bag you may bring, so beware of the cheap deals to lure you in. Be sure to scope out the website and price restrictions/conditions prior to leaving the US in order to ensure you won’t meet any hidden charges or fees. (Note: the website is quite ostentatious and may look a lot like a cheap scam, however I have personally boarded and landed safely in their plane and had a speedier check-in than I’ve ever experienced in the United States.)
Getting to Europe can also be much cheaper than you may imagine. On the note of Ryan Air, if (and when) I choose to travel overseas again, I will look for the cheapest flight to Ireland, the UK or Europe and from that particular destination, will book myself a flight to my desired end point abroad. Keep in mind the baggage rule, but for example, we recently found a roundtrip flight from San Francisco to Dublin for $431. If one were to pack accordingly, you could be in Paris via Dublin for only about $13 more dollars. Also, Iceland has been having some serious financial difficulties as of late so it is right now one of the cheapest airlines to fly on. Their country is being hit hard and everyone is suggesting flying there and then off to other parts of Europe as well.
Thank you, Global Recession!