The Internet - the ability to publish anything, worldwide, instantly.
Google - the ability to search the whole of human knowledge (ok, a close approximation thereof) before you even finish typing the query.
Cellular data - the ability to access the above from nearly anywhere anytime (as I find this thread and publish this response from an iPad while a passenger in a car moving 80MPH, and it's no big deal).
Wikipedia, absolutely (that's also what I answered over there).
I think Wikipedia is often forgotten in discussions about the truly revolutionary companies of the last decade. Probably because they're non profit. But Wikipedia is one of the pinnacle examples of how the combination of technology and entrepreneurship can change the world.
This is so fundamental that it's easy to forget but the hyperlink is truly the most fundamental component of the net.
The beauty of the link is how it tells us that all knowledge is interconnected and that we all are part of the same whole.