Unix
All the best operating systems have an X in their name. Even Windows XP is the best effort to come out of Microsoft. My personal preferences are Sun's version of Unix, Solaris and the community version of Red Hat Linux, Fedora Core.
I've been working with Unix for about 15 years now, first with System V Release 4 running on very obscure Texas Instruments hardware ( the TI-1500 anyone ? ). From there I moved on to SCO's Open Server 5. Of course SCO is massively unpopular now it is trying to generate revenue from threatening Linux users, but at the time (mid '90s) it was a popular and sensible option for running Unix on non proprietary Intel based hardware.
And from there I moved on to Solaris and Red Hat Linux and administering DNS, sendmail, Apache and Checkpoint firewalls, as well as databases. I'm currently employed as a Unix security specialist at dns where I'm very happy.
Note to potential employers my full CV is available on request.
My SCSA cram notes for Solaris 10 part 1 - I passed so they can't be too bad ...
Some links
News sites
All security lists on one site (you don't want this lot clogging up your
mailbox every day)
http://www.derkeiler.com/
General stuff
Sunsite mirrors at Imperial College
ftp://sunsite.doc.ic.ac.uk/
Free online tech books
http://www.techbooksforfree.com/
Sun and other Solaris stuff
Sun's free resource for patches, alerts and documentation
http://sunsolve.sun.com
Sun's BigAdmin portal for administrator's
http://www.sun.com/bigadmin
Solaris Tips and Tricks
http://sysunconfig.net/unixtips/solaris.html
Solaris (in) FAQ
http://www.fixmyfirewall.com/solaris_infrequently_asked_and_obscure_questions.html
Paddy and Jim's Solaris notes
http://www.fixmyfirewall.com/solarisnotes.html
Solaris hardening
http://security.depaul.edu/tools/pub/sol2.6-hardening.txt
The vexatious question of two hard drives and a CDROM in an Ultra 10
http://sunsolve.sun.com/search/document.do?assetkey=1-9-74513-1
Excellent Jumpstart document
http://www.pimpworks.org/sun/jumpstart-howto.html
Sun DiskSuite RAID 0+1 or 1+0
http://www.psychofx.com/chris/unix/sun/dsraid10.txt
Home Projects
Wireless on Linux
http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html
Other technolgies I'm interested in
CVS FAQ-O-Matic
https://ccvs.cvshome.org/fom//cache/1.html
LDAP on Checkpoint firewalls
http://www.checkpoint.com/support/technical/online_ug/firewall-14.0/amarch.htm#936
Old but helpful online guide to Firewall-1. If you can find a more up to
date version then let me know
http://www.checkpoint.com/support/technical/online_ug/