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LinuxQuestions.org offers a free Linux forum where Linux newbies can ask questions and Linux experts can offer advice. Topics include security, installation, networking and much more.

- UNIX and Linux Forums - Learn UNIX, UNIX commands, Linux, Operating Systems, System Administration, Programming, Shell, Shell Scripts

The Linux Documentation Project is working towards developing free, high quality documentation for the Linux operating system. The overall goal of the LDP is to collaborate in all of the issues of Linux documentation.

Computer Help from your Friendly How-To Geek

Linux blog by Vivek - Includes news, help, tutorials, programming, tips and how-to guides for Linux, UNIX, and BSD.

Linux.com - For the community, by the community, Linux.com is the central source for Linux information, software, documentation, how-tos and answers across the server, desktop/netbook, mobile, and embedded areas.

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HowtoForge - Linux Howtos and Tutorials

iRedMail is a free, full featured, easy-to-install, open source email server solution which powered by pure open source software, provides POP3, IMAP, SMTP, anti-virus and advance anti-spam features, works on Red Hat Enterprise Linux, CentOS, Debian ...