Microsoft loves all kind of Insider Programs. You can join the Windows 10 (Mobile), Office and Xbox Insider Program and get early access to new features, give feedback etc.
Starting today, Skype now also has an Insiders Program which will give you early access to Skype Software, new features and improvements. Furthermore, you can give feedback and submit suggestions to the Skype Team to shape and enhance the entire Skype experience.
The Skype Insider Program does not limited on the Skype app for Windows 10. You can also get Preview version for both the Android and the iOS Skype App.
You can sign up here to become a member of the Skype Insider Program.