Welcome to this morning’s edition of “First To Know,” a series in which we keep you in the know on what’s happening in the digital world. Today, we’re looking at three particularly interesting stories.

Microsoft Launches Windows 8 Release Preview

As expected after an accidental leak on one of Microsoft’s blogs, Microsoft has released the Windows 8 Release Preview (RP). This version is an important milestone in the development of Windows 8, as it is probably the last major beta version of the OS before the final one, which should hit stores in late 2012.

Microsoft was kind enough to give us an advance look at Windows 8 RP; read our impressions here.

Samsung Sells 50 Million Galaxy S Devices

Samsung has announced it sold 24 million Galaxy S and 28 million Galaxy S2 smartphones, meaning 52 million Galaxy S devices have been sold to date.

Samsung also did good on the smartphone-tablet hybrid front, selling over 7 million Galaxy Notes so far.

BlackBerry PlayBook OS 2.1 Beta Now Available for Download

Research in Motion has launched BlackBerry PlayBook OS 2.1 beta, bringing improvements for the tablet’s portrait mode — Email, Calendar and Contacts apps are now supported. The update also brings better support for Android apps and full device encryption.

Image courtesy of iStockphoto, mattjeacock

More About: blackberry, features, first to know series, galaxy s, mashable, microsoft, samsung, Windows 8

For more Tech coverage:

• Follow Mashable Tech on Twitter
• Become a Fan on Facebook
• Subscribe to the Tech channel
• Download our free apps for Android, Mac, iPhone and iPad