Here are links to various release notes that may be of interest.
This page contains features released to production in November 2017 and later. Visit Archived SaaS Release Notes to see features released to production through October 2017. Maintenance items for releases 3300.0.0 and earlier can also be accessed in the Archive.
Cumulative Update 1 for Q2 2018 is now available. It emphasizes new privacy protections and enhances to mobile web services.