Use filters to gain direct visibility into the information you need, whether that be Teams, Queues, or Campaigns. For example, case managers can use the Queue view to organize cases for their reps, and marketers can look at Campaigns to get the results on the latest holiday push. Enhanced List View Filtering gives you more ways to sift through your data fast. 
Save time with Mass Quick Actions for most objects. You can now edit or add child records like tasks or comments for up to 100 records in a list view using Lightning Experience. With Mass Quick Actions, updating data and keeping it clean has never been easier. 
Get greater flexibility and control for your navigation using drag-and-drop tools to customize your navigation bar. End users can now easily add and reorder items and tabs. Admins can now enable or disable personalized navigation by app.
Lightning Themes has been enhanced based on your feedback. Now, when uploading images, it's easy to crop the image as needed so you no longer need to upload an exact image resolution. We've also made it possible to override calculated colors, so your themes can reflect the exact colors of your brand.
In the Summer ’18 Release, Lightning Experience stylesheets are generally available for Visualforce pages. Now, developers can control whether a page is styled with the look of Lightning Experience when viewed in Lightning Experience or the Salesforce app by using the lightningStylesheets attribute. Previously, restyling a page for Lightning Experience involved searching the Salesforce Lightning Design System reference site for matching components. The new lightningStylesheets attribute gives unstyled Visualforce pages the Lightning Experience look, automatically.
Accelerate app development with new and improved Lightning Components. With recordForm, you can build a record form, layout, or page in seconds, using only one line of markup. We’ve made other improvements to existing base Lightning Components, including inline edit and Booleans in dataTable, images in inputRichText, and custom SVG icons.