Apache Maven Project (http://maven.apache.org)

The Apache Maven project maintains the official documentation for Maven including essential reference pages for POM and Settings formats. If you have a question about Maven, or if you are looking for detailed reference information about a Core Maven plugin. Check this site first for the latest documentation.

Apache Mailing Lists (http://maven.apache.org/mail-lists.html)

If you are a heavy Maven User, you might find it helpful to sign-up for the Maven Users List. This is a high traffic list dedicated to Maven community support. If you are writing plugins or contributing to the Maven project, you should also sign-up for the Maven Developers mailing list.

Sonatype Blogs (http://www.sonatype.com/people)

Sonatype's focus is to support the Maven eco-system, we frequently write about Maven best practices, news, and emerging trends in the Maven ecosystem. Subscribe to Sonatype's blog to keep up with the latest developments in the Maven community.

Sonatype Books (http://www.sonatype.com/books.html)

Sonatype books are the essential references for anyone working with Apache Maven, repository management, and integrating Maven with Eclipse. In Maven: The Complete Reference, you can explore the details of the POM, Maven Settings, Maven Archetypes. Maven by Example walks you through the key concepts of the world's leading project management tool.​

Apache Software Foundation Projects  http://projects.apache.org

This site is a catalog of Apache Software Foundation projects. It is designed to help you find specific projects that meet your interests and to gain a broader understanding of the wide variety of work currently underway in the Apache community.

All project data is maintained by the individual projects themselves. If you do not find the project you are looking for here, you can browse through the top-level Project Management Committees starting at the Apache Software Foundation homepage. 

About OpenStack - http://www.openstack.org/

OpenStack is a cloud operating system that controls large pools of compute, storage, and networking resources throughout a datacenter, all managed through a dashboard that gives administrators control while empowering their users to provision resources through a web interface.

OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, full-featured, and Open Source toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) protocols as well as a full-strength general purpose cryptography library. The project is managed by a worldwide community of volunteers that use the Internet to communicate, plan, and develop the OpenSSL toolkit and its related documentation.

OpenSSL is based on the excellent SSLeay library developed by Eric A. Young and Tim J. Hudson. The OpenSSL toolkit is licensed under an Apache-style licence, which basically means that you are free to get and use it for commercial and non-commercial purposes subject to some simple license conditions.