While I'm on this break from working, I've been planning some travel, and my new favorite site for open-ended travel exploration is Google Flights. Just enter your starting airport and a start date (and optionally an end date), leave the destination blank, and Google Flights can return you a map of the world with lowest one-way or round trip ticket prices for any destination (I assume this is powered by data from their ITA acquisition).
It looks like this (click it for a larger view).
You can use a price filter slider and drag it down in price to reduce the number of destinations. Now they just need to add in hotel pricing for all-in open-ended travel budgeting.
It's a luxury to be able to plan travel this way, but for those rare times when you can, this is a fun way to do it. I was using this just a few weeks ago and found a random discount fare to Taiwan, and now I'm onboard a flight there.
Once we all are wearing virtual reality goggles we'll undoubtedly be able to spin a virtual globe with this visualization mapped on top of it. Though I suppose, at that point, perhaps we'll just travel places virtually, for much lower prices.