Apple released a public beta of iOS 9 available for everyone who is interested to try it out. In order to participate users need to do is join the Apple Beta Software Program with their Apple ID.
The iOS 9 public beta is a more simplified release than the versions that were available only for developers over the last month. Few days ago, Apple released iOS 9 beta 3 to registered developers.
Apple iOS 9 brings a number of new features and improvements over its predecessor. It includes more capable Siri, split-screen multitasking for iPad, and and many other micro upgrades.
If you are interested in trying out this new version of iOS 9 in open beta, click on the source link to get started. But keep in mind that the firmware is not yet finished, so you may experience bugs and instability.