ClearOS is my SMB server distribution of choice. It works fine out of the box in most cases, but a little CLI work can make the system even better.
Note: on my system, /dev/sda and /dev/sdb are configured in RAID-1 as /dev/md0

Enable SSH access
Add the following to /etc/system/webconfig
allow_shell = 1
You can now enable SSH on a per-user basis via the GUI

Tools
Virtual terminal multiplexer and text-mode browser
yum install screen links
Development tools
yum install kernel-source kernel-headers gcc kernel-sourcecode
yum groupinstall "Development Tools"

Reduce disk usage
Modify /etc/fstab
/dev/md0 defaults,noatime

System and HD sensor packages
HardwareLiSter
wget http://ezix.org/software/files/lshw-B.02.14.tar.gz
tar xvfz lshw-B.02.14.tar.gz
cd lshw-B.02.14
make && make install
System and HD sensors
yum install lm_sensors
sensors-detect
yum install smartmontools
Test everything
lshw
sensors
smartctl --all /dev/sda
smartctl -H /dev/sda
smartctl --all /dev/sdb
smartctl -H /dev/sdb

Enable Atheros AR8131 Gigabit NIC
Download AR81Family Linux Driver from http://partner.atheros.com/Drivers.aspx
Decompress (ignore error messages)
tar zxf AR81Family-linux-v1.0.1.13.tar.gz
Remove NAPI lines from /src/kcompat.h (see http://blog.lkc.idv.hk/?p=338)
Compile and load
make && make install
modprobe atl1e

Add nmap to GUI
wget http://download.clearfoundation.com/community/timb80/app-network-scanning-5.1-1.i386.rpm
yum localinstall --nogpgcheck app-network-scanning-5.1-1.i386.rpm

AJAX Live Log Viewer
rpm -Uvh http://download.clearfoundation.com/community/timb80/app-livelogs-5.1-6.i386.rpm

Network DNS Tools
wget http://download.clearfoundation.com/community/timb80/app-network-tools-5.1-1.i386.rpm
yum localinstall --nogpgcheck app-network-tools-5.1-1.i386.rpm