Required Texts:
UNIX and Linux System Administration Handbook, 4th Edition, Evi Nemeth, et al.

Learning Perl, 6th Edition, Randal Schwartz

Safari Books Online
Other eBooks available through the Knowledge Center

Additional Texts:

Regular Expressions:
Teach Yourself Regular Expressions in 10 Minutes
Regular Expression Pocket Reference
Mastering Regular Expressions, Third Edition
Regular Expressions Cookbook

Systems Administration:
Automating System Administration with Perl
Python for Unix and Linux System Administrators
Pro Python System Administration

Hacks:
Ubuntu Linux Desktop Network Security
Perl PHP SQL Web Site Measurement
Windows Server PayPal Amazon Google

Cookbooks:
Linux bash Shell Scripting Linux Networking Puppet
Web Site HTML5 HTML5 Developer CSS PHP Ruby Rails
SQL MySQL Admin High Availability MySQL
GIMP VMware
PowerShell Active Directory Windows Server