Dr Grohol's PsychCentral includes a twenty question online Obsessive-Compulsive Disorder quiz. After answering the questions, participants are given a score of the likelihood of them having OCD.
While the quiz is not meant to be a diagnostic tool, it can give students a good perspective of OCD. The OCD online quiz can be found at http://psychcentral.com/ocdquiz.htm
The homepage for PsychCentral is at http://psychcentral.com/