few links that I think are relevant and interesting :)

Object-Oriented System Development by Dennis de Champeaux
[link|http://gee.cs.oswego.edu/dl/oosdw3/|http://gee.cs.oswego.edu/dl/oosdw3/]
I never read this one, but I want to read that chapter about ensembles I heard the term used in the tcl community, I have no idea what it means

Object Oriented programming in ansi-c
[link|http://www.cs.rit.edu/~ats/books/ooc.pdf|http://www.cs.rit.edu/~ats/books/ooc.pdf]
I tried to read it, it was too hard for my skill level :(

Objects and classes vs modules
[link|http://pauillac.inria.fr/~xleroy/talks/icfp99.ps.gz|http://pauillac.inri...alks/icfp99.ps.gz]

Mixing modules and objects
[link|http://cristal.inria.fr/~remy/cours/appsem/ocaml-mixins.html|http://cristal.inria...ocaml-mixins.html]

This Objective-c book has one of the best introductions to OOP
[link|http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/ObjC.pdf|http://developer.app...jectiveC/ObjC.pdf]


And this free UML book offer in my opinion one of the best intro to Object Orientation
[link|http://www.ariadnetraining.co.uk/UML%20Applied%20Companion.zip|http://www.ariadnetr...d%20Companion.zip]
check their website for more detail on a newer to be released version
[link|http://www.ariadnetraining.co.uk/books.htm|http://www.ariadnetr...g.co.uk/books.htm]

In my opinion the Objc book and UML book are the best intro to OO you will ever find

Good luck