The simplest solution that I've seen for shared contacts in gmail. e.g. I can create a contact group named "investors" and share it with my colleague. Then as I add/remove contacts from it, it's updated automatically on their end. It's frankly insane that Google Apps doesn't have this functionality built in.

The company I founded, @newmindgroup has sold, deployed and serviced 100s of Google Apps domains over the last several years. Clients are consistently perplexed that Google has not included this functionality by default in the product. I've seen this product before and every time I do I roll my eyes. :\ End rant. :)

In 2020 if you are looking for the best options then you must have tried www.contactbook.app one of the best contact sharing application.

We used to have Shared Group but it didn't work well the past years so we switched to the app Shared Contacts for Gmail: www.gmailsharedcontacts.com and have been very satisfied with it. It allows you to create a label (contacts group or distribution list), organize it, share it with your colleagues directly from Google Contacts Managers and set different access levels, exactly like you do when you share a Google Doc. Their support team is extremely responsive which is very appreciable. It is easily foundable on the Chrome Webstore and on the G Suite marketplace.

Simple and could be useful for many different use cases.

Other nice and even more simple solution ---> www.gmailsharedcontacts.com/

There is a newer app that is better and is working for us: https://shareemailcontacts.com