I received this request:

“A faculty member would like her students to be able to indicate which thing posted by other students are the most interesting — so something like being able to vote on or ‘like’ posts.”

and installed wti-like-post. Enjoy. -Tim

4/21/2014 UPDATE: The plugin did not work as expected and has been uninstalled. The wordpress plugin repository has thousands of plugins and some of them don’t work as described so this is not a surprising result.