Apache HTTP Server : Open Source HTTP Server.
Apache Abdera : Open Source Atom Implementation.
Apache ActiveMQ : Open Source Messaging and Integration Patterns Provider.
Apache Ant : Automation Build Tools.
Apache APR : Portable Runtime Project.
Apache Archiva : The Build Artifact Repository Manager.
Apache Avro : Data Serialization System.
Apache Axis : Web Service Container.
Apache Buildr : Build System for Java-based Applications.
Apache Camel : Open Source Integration Framework.
Apache Cassandra : High Scalable Second-Generation Distributed Database.
Apache Cayenne : Object Relational Mapping, Persistance and Caching for Java.
Apache Chemistry : Content Management Interoperability Services (CMIS) Implementation.
Apache Click : Modern Web Application Framework.
Apache Cocoon : Spring-based framework built around the concepts of separation of concerns and component-based development.
Apache Commons : Common Libraries. (Attributes, BeanUtils, Betwixt, Chain, CLI, Codec, Collections, Compress, Configuration, Deamon, DBCP, DbUtils, Digester, Discovery, EL, Email, Exec, FileUpload, IO, JCI, Jelly, Jexl, JXPath, Lang, Launcher, Logging, Math, Modeler, Net, Pool, Primitives, Proxy, Sanselan, SCXML, Transaction, Validator, VFS)
Apache Continuum : Continuous Integration and Build System.
Apache CouchDB : Document-oriented database that can be queried and indexed in a MapReduce fashion using JavaScript.
Apache CXF : Open Source Services Framework.
Apache DB : Embedded Database.
Apache ESME : Enterprise Social Messaging Environment.
Apache Felix : OSGi R4 Service Implementation Platform.
Apache Forrest : Various Sources Publishing Framework.
Apache Geronimo : Fully certified Java EE 5 application server runtime.
Apache Gump : Oldest Continuous Integration Tool.
Apache Hadoop : (HDFS, Common, MapReduce)
Apache Harmony : Modular Java runtime with class libraries and associated tools.
Apache HBase : Hadoop Database.
Apache Hive : Data warehouse system for Hadoop.
Apache HttpConponents : (Core, Client, AsyncClient, HttpClient)
Apache Jackrabbit : Fully conforming implementation of the Content Repository for Java Technology API (JCR)
Apache Jakarta : Offers a diverse set of open source Java solutions. (BCEL, BSF, Cactus, JMeter, JCS, Regexp)
Apache James : Delivers a rich set of open source modules and libraries, written in Java, related to Internet mail communication which build into an advanced enterprise mail server.
Apache Karaf : Small OSGi based runtime which provides a lightweight container.
Apache Lenya : Open Source Content Management (Java/XML)
Apache Logging : Logging of application behavior and released at no charge to the public. (Log4*)
Apache Lucene : Open Source Search Software.
Apache Mahout : Scalable machine learning library that supports large data sets.
Apache Maven : Management and Comprehension Tool.
Apache Mina : Network Application Framework.
Apache MyFaces : Hosts several sub-projects relating to the JavaServer™ technology.
Apache Nutch : Open Source Web-Search Software.
Apache ODE : (Orchestration Director Engine) executes business processes written following the WS-BPEL standard.
Apache OODT : Metadata for Middleware.
Apache OFBiz : Open Source Enterprise Automation Software.
Apache OpenEJB : Embeddable and lightweight EJB 3.0 implementation.
Apache OpenJPA : Stand-alone POJO persistence layer or integrated into any Java EE compliant container and many other lightweight frameworks.
Apache OpenWebBeans : ASL-licensed implementation of the JSR-299 “Contexts and Dependency Injection for the Java (TM) EE platform” specification.
Apache PDFBox : Java PDF Library.
Apache Pig : Platform for analyzing large data sets that consists of a high-level language for expressing data analysis programs, coupled with infrastructure for evaluating these programs.
Apache Pivot : Open-source platform for building installable Internet applications (IIAs).
Apache POI : Java API for MS Documents.
Apache Portals : Providing robust, full-featured, commercial-quality, and freely available Portal related software on a wide variety of platforms and programming languages.
Apache Qpid : Cross-Platform Enterprise Messaging System.
Apache Roller : Multi-user and group-blog server suitable for blog sites large and small.
Apache Santuario : Providing implementation of the primary security standards for XML.
Apache ServiceMix : Open Source Integration Framework.
Apache Shindig : OpenSocial Container.
Apache Shiro : Java Security Framework.
Apache Sling : Innovative Web Framework.
Apache SpamAssassin : Spam Email Filtering Framework.
Apache STDCXX : Standard C++ Libraries.
Apache Struts : Free open-source framework for creating Java web applications.
Apache Subversion : Enterprise-class centralized version control for the masses.
Apache Synapse : Lightweight and high-performance Enterprise Service Bus (ESB).
Apache Tapestry : Component oriented framework for creating dynamic, robust, highly scalable web applications in Java.
Apache TCL : Tcl-Apache integration framework.
Apache Thrift : Scalable cross-language services development framework.
Apache Tika : Content Analysis Toolkit.
Apache Tiles : Templating framework built to simplify the development of web application user interfaces.
Apache Tomcat : Open source software implementation of the Java Servlet and JavaServer Pages technologies.
Apache Traffic Server : Fast, scalable and extensible HTTP/1.1 compliant caching proxy server.
Apache Turbine : Servlet based framework that allows experienced Java developers to quickly build web applications.
Apache Tuscany : Simplifies the task of developing SOA solutions.
Apache UIMA : Thriving community of users and developers of UIMA frameworks, tools, and annotators, facilitating the analysis of unstructured content such as text, audio and video.
Apache Velocity : (Engine, Tool, DVSL, Texen, Anakia, Docbook)
Apache Wicket : Lightweight component-based web application framework.
Apache Xalan : Collaborative software development project dedicated to providing robust, full-featured, commercial-quality, and freely available XSLT support on a wide variety of platforms.
Apache Xerces : Parsing, validating and manipulating XML docs library.
Apache XML : Crimson, Xindice sub-projects.
Apache XMLBeans : Accessing XML by binding it to Java types.
Apache XMLGraphics : Conversion of XML formats to graphical output. (Batik, FOP sub-projects)
Apache ZooKeeper : Maintaining configuration information, naming, providing distributed synchronization, and providing group services.