Google+ announced today that it is adding a recommendations feature to the +1 buttons used across the web.
When users hover over a +1 button on a website, they will be shown other content from that domain, or sub-domain, that they think you would like.
Here is an example of what it looks like when you hover over a +1 button on Search Engine Journal:
This new feature is rolling out to all users, but initially will show to anyone who is signed up for the developer preview group. So if you cannot wait to try it out, make sure to sign up for the group and check it out.