The original Google Contributor was a novel idea. It allowed users to pay a small amount every month to show fewer ads on their favorite sites (at least Google AdSense ads), while still supporting the sites financially. After launching in August 2015 and never becoming available outside the United States, it was shut down while Google worked on a "new and improved" version.

Now Google has started signups for the new Google Contributor, via this form. Once you submit your email, you will be notified when the service becomes available.

The landing page still shows "early 2017" as the launch date, so hopefully we won't have to wait much longer for a wide release.

Source: Google Contributor