Fedora is a fast, stable, and powerful operating system for everyday use built by a worldwide community of friends. It's completely free to use, study, and share.
Red Hat is the world's leading open source technology solutions provider with offerings including Red Hat Enterprise Linux, open source applications.
CentOS -- Community ENTerprise Operating System is a free rebuild of source packages freely available from a Prominent North American Enterprise Linux.
SL is a Linux release put together by Fermilab, CERN, and various other labs and universities around the world. Its primary purpose is to reduce duplicated effort of the labs, and to have a common install base for the various experimenters.

HOWTOs - Hardening - Security Tips - Security Projects

News and Security Alerts

If you're new to Perl, you should start with perlintro, which is a general intro for beginners and provides some background to help you navigate the rest of Perl's extensive documentation.

php, perl and other script install and upgrade steps.

What should I do, when the server is failing.

RPM Package Manager- rpm is a powerful Package Manager, which can be used to build, install, query, verify, update, and erase individual software packages. A package consists of an archive of files and meta-data used to install and erase the archive files. The meta-data includes helper scripts, file attributes, and descriptive information about the package. Packages come in two varieties: binary packages, used to encapsulate software to be installed, and source packages, containing the source code and recipe necessary to produce binary packages.

The LAMP Stack - Apache, PHP, MySQL, Nginx