Escaping from Google Contacts 

Use Google Takeout to get a copy of all of your Google Contacts or Google+ Circles in either vCard, CSV, HTML, or PDF format.

Escaping to Google Contacts 

Contacts makes it very easy to export data.  Visit the main contacts page directly, or within Gmail.  At the right near the top are links called Import, Export, and Print.  Click the Import link to initiate the import process.

Keeping in sync

Often, you don't want to escape completely in either direction, but rather maintain up-to-date versions of your contacts in more than one system.  The Google Sync Services page tells you how to do this.