Some interesting ideas in this article about why students do and don't use office hours, and ways to make your office hours more convenient and less threatening. The idea of offering topical group "office hours" struck me as particularly interesting... maybe office hours would seem less threatening if they weren't always one-on-one.
The author says "information that is best determined collaboratively with students, should not be prescribed by the professor on day 1." What do you think of his examples?