some things I've added to my own checklist
-confirm kernel is similar to other systems if you comparables
-if it's a production system, set yum or apt to notify you of updates, NOT to install
-check cron for unknown jobs. decide if they're pertinent
-add users to the /etc/passwd and /etc/groups so your UID/GIDs are synchronized
-test CPU with F@H
-test IO somehow
-reboot the system about 20 times to see if you can blow a component(confirm kernel changes, routing tables, etc are persistent)
-confirm your disk layout corellates to what you're paying for, including block sizes, fsck upon boot, etc.
-if networked with other systems consider updating hosts file
-schedule an external security scan
-schedule log rotations
-check for SUID/SGID files, no-owner files and world writable files
-check TCP/IP hardening
-if you can check RAID status from software then schedule it to notify you
-ensure root pwd is needed for entering single user mode and that ctrl-alt-del is disabled.
Thanks,
Dan
http://www.danieljdoughty.com