Yale University Science Libraries came up with a great idea. From now, you can contact one of their librarians through Meebo, GTalk, AIM, MSN, etc. Here is a screenshot of the widget:

Reference service is intended to assist the academic research of students, faculty, and staff of Yale University. If you are not affiliated with Yale, we can reply to your question only if it concerns the University or some unique resource of the University Library: Please send an email to science dot reference at yale dot edu.

The Science Libraries Reference staff will attempt to respond to questions by the end of the following business day. A Reference Librarian is available at the Kline Science Library during regular business hours (Monday - Friday, 9:00 a.m. - 5:00 p.m.).

I wish the library of my university did the same…