There is no set rule on when to expect the topic. Do you already have a date and time setup?
In my experience, the successful candidates addressed the topic without regurgitating other's ideas, engaged the entire audience by looking at everyone, answered questions well, knew their presentation as if they had given it hundreds of times, and related it somehow to the needs of the hiring organization.
I would be surprised if many candidate presentations made it to slideshare. Just thing of presentations you have seen. What did you like or dislike?
Brian C. Gray
Head of Reference & Engineering Librarian
Kelvin Smith Library
Case Western Reserve University
http://blog.case.edu/bcg8bcg8@case.edu