Peter Diamandis, founder of the X Prize Foundation and author of "Abundance" has the best answers to this question, I believe. He and award winning science writer Steven Kotler document dozens of exponentially growing technologies will transform our world in the next 20 years.
Beyond the great strides being made in transforming polluted water (Slingshot is an example) and other ways to clean up our wonderful planet, personally I'm pretty excited about how the growth of cell phone use is fueling microfinance, and vice versa. Both are creating greater intraclass opportunities - which translates as the average person being able to create personal income without relying on the rich for jobs.
A low-cost, handheld medical device (the Qualcomm Tridcorder) that allows the user to self diagnose themselves better than a board-certified doctor sounds pretty exciting, too.