linux:
http://www.userlocal.com
http://linux.box.sk
http://www-136.ibm.com/developerworks/linux/
http://www.learninglinux.com/
http://www.linuxsecurity.com/
http://linuxdocs.org/
http://www.oreillynet.com/linux/cmd/
http://www.justlinux.com/
http://www.linuxquestions.org/
BSD:
http://bsdvault.net/
http://www.freebsd.org/
http://www.unixhideout.com/index.uhc?p=home

These are some of my favorites. Also check out your cities LUG(linux users group).
Mine is the MDLUG(metro detroit linux users group). They always are more than willing to help young linux enthusiasts, some will even offer free onsite installation to help get you going.