Objectify-Appengine is a thin Java wrapper around Google App Engine's low-level datastore API that allows you to persist type-safe POJO objects. It provides a human-friendly query interface, generified key, query, and prepared query classes, GWT-able entity objects, and transactions in one lightweight jar file with no dependencies.
Tephlon is an easy PHP persistence library. It has a highly modular OOP design and a no-SQL storage system. It stores any object or variable safely and tidily on disk for fast access. The API is meant to be easy and fast to learn. It features Java-style key-value maps, namespaces, easy Codeigniter integration, programmable lifetime of records, a multi-driver architecture, reliable and well-tested code, and easy incremental backup of data with SVN or GIT.
persistence4j is a small and lightweight Java object persister that uses JDBC to persist data into a relational database. The library frees you from writing the Data transfer objects - just create a POJO and simply save it. Transactional and non-transactional connections are supported and can be configured from the simple properties file.
Athena Framework for Java is a full fledged enterprise object-relational mapping (ORM) framework that employs metadata as mapping configuration. It greatly simplifies Java Web application development by removing the requirement of manual mapping and manual database schema updating. In addition to features like Java object persistence, powerful EJBQL querying execution, and comprehensive code generation, Athena has built-in support for multi-tenancy, which enables developers to build cloud applications easily. Athena can be easily integrated with other libraries like Struts or Spring to provide full stacks of service.
KiokuDB is a frontend to various data stores. Its purpose is to provide persistence for "regular" objects with as little effort as possible, without sacrificing control over how persistence is actually done, especially for objects that are harder to serialize. KiokuDB is also non-invasive: it does not use ties, AUTOLOAD, proxy objects, sv_magic, or any other type of trickery. Many features important for proper Perl space semantics are supported, including shared data, circular structures, weak references, tied structures, etc.
Wikitty is a key/value storage and search system. A Java object or a relational table is frozen when writing code or creating a database. To make them evolve, you have to go back into the code, write a migration process, etc. It is also hard to maintain coherent code when you want to develop the same application for similar needs with only small differences. Between the common code and the specific code, it can easily become a real burden. Wikitty tries to answer those problems, bringing a technical solution which is easy to put into place and to use.