The following is a list of security and hardening guides for several of the most popular Linux distributions.
Fedora 19 Security Guide by Fedora
Linux Security Checklist by SANS
Oracle Linux 7 Benchmark by CIS
Red Hat Enterprise Linux 7 Security Guide by RedHat
Red Hat Enterprise Linux 7 Security Benchmark by CIS
Red Hat Enterprise Linux 7 Security Technical Implementation Guide by DISA
Red Hat Enterprise Linux 7 Installation Hardening Checklist by GIAC
Red Hat Enterprise Linux 6 Security Guide by RedHat
RedHat Enterprise Linux 6 Security Benchmark by CIS
Red Hat Enterprise Linux 5 Security Benchmark by CIS
Red Hat Enterprise Linux 5 Secure Configuration Guide by the NSA
Slackware 10 Security Benchmark by CIS
SUSE Security and Hardening Guide
SUSE Linux Enterprise Server 12 Security Benchmark by CIS
SUSE Linux Enterprise Server 11 Security Benchmark by CIS