Dynamic Campaigns by Sigstr - Share the most relevant content in every email

Workona - A better way to work in the browser.

PushMarket - Automate personalized emails for ecommerce (YC15)

OneTab - Whenever you find yourself with too many tabs, click the OneTab icon to convert all of your tabs into a list. When you need to access the tabs again, you can either restore them individually or all at once.

InboxSDK - First usable API to write Gmail Apps for 1B active users

Session Buddy - Manage Your Browser Sessions