Post from Google Keep to Google+

At this time, the web app of Google Keep doesn't have a button to share notes somewhere else, but there is a one to copy the note to a new Google document. From there you could share the document using Google+, Twitter, Facebook, and to get the URL to share the document using other tools.

From Create Google Docs from Keep notes on the web - Keep Help

Create Google Docs from Keep notes on the web Do more with your ideas by copying notes into a Google Doc, where you can expand, edit, and polish your ideas.

To copy one note into a Google Doc:

• Hover over the note you want to add and click the Menu .
• Select “Copy to Google Doc.”

To copy multiple notes into a Google Doc:

1. Hover over each note you want to add.
2. For each note, click the check mark .
3. In the gray action bar at the top, click the Menu .
4. Select “Copy to Google Doc.”