I can certainly add my voice to those recommending TheDamian's insightful OOP book. I'm about three-quarters of the way through and am learning a great deal about Perl, OOP and programming in general. At least I think I am, I guess I'll find out when my head stops going round %-)
Another source you might like to look at is Bruce Eckel's website, where he has copies of his books Thinking in Java and Thinking in C++ available for free download. They will give you some insight for OOP in other languages.
