Here is the release overview presentation with screenshots highlighting the important features and functionalities introduced in Salesforce Summer 16 Release
For videos, release notes and other resources on Summer 16, please navigate to URL http://www.salesforce.com/customer-resources/releases/summer16/
And here is the link to some great blogs summarizing the useful features in Summer 16 release
- http://www.jitendrazaa.com/blog/salesforce/summer-16-top-features
- https://blog.force365.com/2016/04/30/salesforce-summer-16-platform-highlights
And here is the list of past release overview decks