This week's Windows 10 Mobile entry in the Fast ring is Insider Preview build 15047. There aren't many new features, but there are plenty of fixes and improvements, and one known issue.
Build 15047 RSS
Microsoft today released a pair of Windows 10 Insider Preview builds to the Fast ring, which are 15048 for PCs and 15047 for phones. They're light on new features, since there was a build on Tuesday.