One of the things that took me a long time to figure out is that often, flying through 2-3 different cities on a single ticket often costs very similar to a one-way flight.
So, going "New York to Berlin on May 25th" might not be cheaper than going "New York to London on April 28th, London to Munich on May 22nd, Munich to Berlin on May 25th" -- strange but true.
It's especially easy to stop in hub cities for up to a month, so swinging through Chicago, New York, Los Angeles, London, Tokyo, Hong Kong, and other regional hubs is easy. It's fun to stop in New York for 2-3 days when you're on your way elsewhere if you've got the time.
The thing is, it can be tricky to plan these routings. That's where Matrix comes in --
People don't link to it much, since you can't book directly from it. But it's incredibly useful at figuring out interesting flight routes -- they've got most of the spectrum of possible flights covered except possibly some discount carriers.
Matrix is robust: it's the back-end for most of the flight search engines like Orbitz and Kayak. Again, you can't book directly from it, but it lets you piece together which cities and dates coordinate well together.
My favorite feature on it? You can click the "Nearby" link next to any airport you enter, and search airports within a large possible range of nearby airports. If you want to really go crazy, you can search something like "within 500 miles of this airport" -- so if you just want to land on Continental Europe, in Japan, or anywhere in China, you sometimes find cheap, fun, or available fares to airports you never would have guessed to go on your own. Then you can grab rail or a discount flight to get to whatever city you wanted to start from.
It's probably not the best tool for new travelers -- I'd recommend you start with kayak.com or kayak.com/explore (which has a wonderful "where can I go for how much?" feature from any airport, which is easy to use and great).
But once you're starting to get into more advanced travel, definitely check out Matrix. You can do some really cool things with it once you get the hang of it.
You're absolutely right. matrix is a great tool. However for flights in Europe check out skyscanner.com (it's german but you can change language and currency at the top). The great thing about it is that it also searches low-cost carriers like Ryanair that don't show up in matrix.
You can get your scuba licenses and go on some crazy dives for $500 total, or less.
Learn to snowboard? $500, again, give or take.
Fly an airplane? Look it up. It ain't so much.
International travel? Trivially easy and inexpensive in the days of Skype, Matrix ITA flight search + kayak.com, Wikitravel, and Google.
That list of stuff you're "going to get to someday"?
I was in Berlin for an extended weekend recently, and the whole time I found myself agreeing again and again with what I had read about the city in Maneesh's (hackthesystem.com) post about it. It's a great post and introduction to Berlin, even if he oversells his reasons a bit. Below is his article, with some of my additional thoughts in italics.
It had been a long time since I’d stayed in one city for so long, but I’d engineered it so I could spend my final quarter of Stanford abroad…and receive financial aid at the same time. I’d heard nothing but great things about Berlin, and when Stanford offered me a paid summer internship, meaning I’d be living scot free in the city, I couldn’t say no.Within weeks of arriving, I understood why Berlin had received so much praise—the only other city I’ve ever seen as revered is Buenos Aires. Let me tell you now exactly why you should log on to kayak.com and buy a ticket to Berlin, Germany.
I was blown away when I saw the prices in Berlin. Living expenses are as cheap, or cheaper, than most cities in South America! (Buenos Aires included). I could afford dinners an the nightlife—Berlin is by FAR the cheapest capital city in Western Europe. Here are some examples of my costs (everything is converted into dollars at 1 € = $1.50)
[Side note: one time I only had 1EUR on me, and I entered a gas station to buy water. Water cost € 1.25. Beer cost € 0.60. Needless to say, my decision was made for me]