pgstream is a C++ library that is built on top of libpq for PostgreSQL v7.4 or higher. It aims at providing programmers an easier interface than the libpq C API when using C++. It provides classes that support parameterized queries, exceptions for catching database errors, transactions and subtransactions, reading and writing bytea columns, using prepared statements, SQL cursors, and more.
Manitou-Mail is a 3-part database-driven email system: a PostgreSQL database for the storage engine, a Perl daemon that does send/receive and customizable analysis/indexing of the mail, and a mailer-like user interface (C++/Qt) connected to the database. The general goal is to provide a database-style architecture to handle email, not just for storage but at the application level too. Fast and shared access, fine-tuned security, robust storage, consistent backups, auditing, statistics, and customized add-ons are possible.