Apple held a live event yesterday. You can catch the whole thing at www.apple.com/apple-events/september-2015/ otherwise, hit the highlights with the official videos below.
https://www.youtube.com/watch?v=wGe66lSeSXg
https://www.youtube.com/watch?v=aBYWGjIzvyw
https://www.youtube.com/watch?v=cSTEB8cdQwo
https://www.youtube.com/watch?v=lLlgSawI2Jw
iOS 9 will release to the public on September 16 and OS X 10.11 El Capitan will come available on September 30th.