The ASF is made up of nearly 150 top level projects which cover a wide range of technologies. Chances are if you are looking for a rewarding experience in Open Source, you are going to find it here.
Apache Camel is a powerful open source integration framework based on known Enterprise Integration Patterns.
Apache Camel is a powerful open source integration framework based on known Enterprise Integration Patterns. Rules for Camel's routing and mediation engine can be defined in either a Java based DSL, XML or using DSLs for dynamic languages such as Groovy or Scala.
Java Persistence API Implementation
Apache OpenJPA is a Java persistence project at The Apache Software Foundation that can be used as a stand-alone POJO persistence layer or integrated into any Java EE compliant container and many other lightweight frameworks, such as Tomcat and Spring. The 1.x releases are a production ready, feature-rich, compliant implementation of the Java Persistence API (JPA) 1.0 part of the JSR-220 Enterprise Java Beans 3.0 specification, which pass the Sun JPA 1.0b Technology Compatibility Kit. The 2.x releases are a production ready, compliant implement of the JSR-317 Java Persistence 2.0 specification, which is backwards compatible to the JPA 1.0 specification...