Google introduced a new feature that lets you search, listen and share your favorite Youtube videos without leaving G+.
Mouse over the Youtube icon at the top right of your G+. Then search for your favorite videos in the search field and click play. A playlist with your search results will open in a separated popup window. Also you can control the play with the Pause/Play that shows at the top right of your G+ window.
You can +1 and share your favorite videos, by clicking the +1 and the "Share" button in the popup window.
See attached images. Enjoy!