Google which owns ITA Matrix has revamped its Google Flights tool which has been around for a few years but has a better interface and is faster than ITA. It also lets you click on the fares and pull up the actual itinerary on the airline's site. As with any airfare with multiple airlines involved, one has to double check to make sure that the routing and times are valid. You can get help with choose multiple destinations or just typing in a continent and seeing airfares to that
https://www.google.com/flights/
Here is some background and tips from the official Google blog.
http://googleblog.blogspot.hk/2015/02/get-away-with-google-flights.html