Gentle.NET is a CLS-compliant, database independent object persistence framework. It has an extensive feature set, excellent performance, and reasonably complete docs. It features automatic SQL generation, object construction/caching/uniquing, validation, bindable list support, relation management, transactions, and much more. Oracle, PostgreSQL, MySQL, Firebird/InterBase, MS SQL Server (incl. CE), MS Access, SQLite, Sybase, and Sybase ASA are supported. It includes a NAnt build file as well as VS.NET project files for building under Windows. Mono 1.1.4 and higher is fully supported.
SDE for NetBeans is a UML modeling environment tightly integrated with NetBeans. It lets you draw all types of UML diagrams (use case diagram, class diagram, sequence diagram, activity diagram, etc.) in NetBeans, reverse source code (Java, C++, XML, XML Schema, CORBA IDL, etc.) to UML models, and generate Java source from UML diagrams. It features a Rational Rose importer, an XMI importer, HTML/PDF documentation generators, and plug-in and template support.
SPOPS (Simple Perl Object Persistence w/ Security) is a robust and powerful Perl module that allows you to serialize objects. It is unique in that it also allows you to apply security to these objects using a fairly simple but powerful scheme of users and groups. It's also unique in that for most objects, you will not need to write any code. All you need is a fairly simple configuration file, and you can have a class for your object ready to go, right out of thin air.
Ice is a modern alternative to object middleware such as CORBA or COM/DCOM/COM+. It is easy to learn, yet provides a powerful network infrastructure for demanding technical applications. It features an object-oriented specification language, easy to use C++ and Java mappings, a highly efficient protocol (including protocol compression), asynchronous method invocation and dispatch, dynamic transport plug-ins, TCP/IP and UDP/IP support, SSL-based security, a firewall solution, and much more.
COID is an object-oriented networking library with a tool that automatically generates a lightweight communication layer directly from a C++ class declaration. The coidgen tool automatically extracts designated classes and methods from specified header files and generates a corresponding client class and host dispatcher. The server library manages networked and local connections and provides various services to running objects. The communication layer establishes either remote connection through TCP or direct (vtable) connection between the client and the server (if they reside in the same process).