see also: http://ubuntuforums.org/showthread.php?t=842775

yum install i8kutils.x86_64

Enable startup at boot:
chkconfig i8k on
echo "#!/bin/bash" >> /etc/rc.d/rc.local
echo "" >> /etc/rc.d/rc.local
echo "/bin/su jeff -c \"/bin/i8kmon -a -d &\"" >> /etc/rc.d/rc.local
chmod +x /etc/rc.d/rc.local
echo "set config(0) {{- 0}  -1  55  -1  55}" > /home/jeff/.i8kmon
echo "set config(1) {{- 1}  45  65  45  65}" >> /home/jeff/.i8kmon
echo "set config(2) {{- 2}  55  75  55  75}" >> /home/jeff/.i8kmon
echo "set config(3) {{- 2}  65 128  65 128}" >> /home/jeff/.i8kmon

Example ~/.i8kmon config file:
set config(0) {{- 0}  -1  55  -1  55}
set config(1) {{- 1}  45  65  45  65}
set config(2) {{- 2}  55  75  55  75}
set config(3) {{- 2}  65 128  65 128}

Example 2 ~/.i8kmon config file:
set config(0) {{- 0}  -1  60  -1  65}
set config(1) {{- 1}  50  70  55  75}
set config(2) {{- 2}  60  80  65  85}
set config(3) {{- 2}  70 128  75 128}

Start manually:
/usr/sbin/modprobe i8k force=1

man i8kctl
man i8kmon

Automatically monitor CPU temps and adjust fan speed:
i8kmon -a -d

Manually set fan to low
i8kctl fan - 1

Manually set fan to high
i8kctl fan - 2

Manually turn fan off
i8kctl fan - 0