There are some great sysadmin resources spread across the internet, but it can be difficult to find them in the morass.
Here are some I have recently stumbled across.
Useless Use of * – a presentation originally given at SCALE 2007 by Jan Schaumann
Teaching System Administration in the Cloud, ;login, The USENIX Magazine, October 2010 also by Jan Schaumann
Other good miscellaneous resources by Jan Schaumann
More for new users but always a good refresher: Getting Started with SSH by Kimmo Suominen
Proxy through SSH by Kimmo Suominen
Tom Limoncelli’s youtube videos about Time Management for Sysadmins