Steve Jobs announced the golden master candidate of the iOS4 for developers at the ongoing WWDC 2010. The Golden Master candidate of the iOS4 will be available effective immediately to all the developers. The final version of the iOS4 will be released sometime soon. Developers can download the golden master candidate of the iOS4 by logging in to their developer account.
Here is the link to download the iOS4 Golden Master firmware. The iOS4 brings many new features with it like multitasking, Folders, integrated Retina Displaysupport, and an updated camera and photos application.
The iOS4 will be available as a free update for the iPhone 3G and iPhone 3GS owners. All iPod touch owners, except the first generation, are also eligible for a free update to the iOS4 update. The iOS4 update for these iDevices will be released on June 21st.
Sadly, Apple did not mention when the iPad will get some iOS4 love.