Mjølner System
An Object-Oriented multi-platform rapid application development environment.
http://www.daimi.au.dk/~beta/mjolner_system/

Object-Oriented Forth Survey
ACM SIGPLAN article by 2 academics surveys, summarizes, and compares 17 OOFs.
http://www.zetetics.com/bj/papers/oofs.htm

JAOO
Information on annual European conference on Java and object-oriented software engineering.
http://www.jaoo.dk/

Osage
Object-Relational mapping for JDBC databases, with XML features. [Open Source, LGPL]
http://osage.sourceforge.net/

SimpleORM
Implement, low overhead object/relational mapping on top of Java JDBC. [Open source]
http://www.simpleorm.org/

TopLink
Object-relational bridge by Oracle. Quick tour, tutorials, and howtos. [Commercial]
http://www.oracle.com/technology/products/ias/toplink/index.html

ReportWeaver
Enterprise report writing solutions
http://www.qint.de/

XLISP
A superset of the Scheme dialect of Lisp with extensions to support object-oriented programming.
http://www.mv.com/ipusers/xlisper/

Object-Oriented Programming in Oberon-2
Tutorial with history, descriptions, code samples, references.
http://statlab.uni-heidelberg.de/projects/oberon/kurs/www/Oberon2.OOP.html

MercuryBoard
Bulletin board written in object-oriented PHP4 with a MySQL database backend.
http://www.mercuryboard.com/