Users love Single Sign-On, and deep integration makes users happy, because it helps them avoid entering duplicate data and makes useful information accessible from their day-to-day communication and collaboration tools. To help you discover ways to integrate your own apps with Google Apps, Google added a "new section to developer docs showcasing examples from popular applications in the marketplace."
Some examples, like BatchBook's streamlined sign-up process for users, show simple ways applications can help users get started quicker.
Apps can help users be more productive by displaying information and allowing them to take action right within an e-mail message. You'll also find examples for collaboration and document sharing, such as Manymoon's seamless integration with Google Docs. This makes it easy for users to share information with teams or attach relevant docs to tasks.
More Info: Integrations