Today (Oct 28, 2015, Microsoft corporate VP Joseph Sirosh announced the latest update for the SQL Server 2016 Community Technology Preview (CTP) 3.0. ( See SQL Server 2016: Everything built-in). The download has been released week during the PASS Summit - and is now available. You can find it here - SQL Server 2016 CTP Download.
On March 7, 2016, the first Release Candidate (RC0) is available. You can find it here: SQL Server 2016 Release Candidate 0.