Based on information originally provided by Brian Marick:

Books that include some discussion of testing OO programs:
    Binder, _Testing Object-Oriented Systems_
    Jacobson, _Object-Oriented Software Engineering_
    Marick, _The Craft of Software Testing_
    McGregor, _Object-Oriented Software Development_
    Siegel, _Object Oriented Software Testing_

There are a vast number of articles about testing OO programs.  I
suggest starting with the September 1994 Communications of the ACM,
which is devoted to this topic.  Chase references.   The February 1996
issue of Object has a piece on system testing with use cases.

Conferences like STAR and Quality Week and Pacific Northwest Software
Quality Conference seem to always have papers on this topic.  I
suggest going to a conference and buttonholing people.

Web sites with discussion:
    <http://www.cs.washington.edu/homes/gmurphy/testSTApp.html>
    <http://www.testing.com/>
    <http://www.toa.com>

Courses on testing object-oriented code (one by Robert Binder,
one by Ed Berard) are described in the Testing Courses FAQ.  Also,
a new addition is an offering from Software Quality Engineering.