There are literally hundreds of thousands of websites devoted to Linux.  I can't list them all here, but I will provide some quick n dirty help for the admin in need.

LinuxQuestions.org - the name itself is enough

While a bit old, the RUTE is still the best way to learn linux.

Search amazon.com for RHCE books

If you just want some cheat sheets to print out, here you go.

Package Management - YUM and RPM are the 2 commands to know

Linux Command Line - Cheat Sheet One, Two, Three