First, look if the lm_sensors package and snmp have already been installed:
rpm -qa | grep lm_sensors
It should return something like
lm_sensors-2.8.1-1
If nothing comes up, you'll have to install the lm_sensors rpm, it should be available through one of the fedora mirrors, and should be called something like: lm_sensors-2.8.1-1.i386.rpm and lm_sensors-devel-2.8.1-1.i386.rpm..

Same story with snmp, you'll need the SNMP packages like: net-snmp-devel-5.1-2.1, net-snmp-utils-5.1-2.1 and net-snmp-5.1-2.1.. (version can vary of course ;)

We'll want snmpd (the snmp daemon) to start at bootup, we can use the setup utility for that, or just type chkconfig snmpd on
Next time you'll reboot snmpd will automatically start too..

Now to configure your sensors, in order for lm_sensors to know which type and vendor sensors your motherboard and system casing is using, you'll need to execute: /usr/sbin/sensors-detect
You'll now be provided with a whole range of detections and questions, you can default the most with yes, if all goes well, it'll load some modules needed to read out your sensor data, and save it to /etc/sysconfig/lm_sensors

We'll also need to copy the initscript for lm_sensors to the bootup scripts directories, issue the command: cp /usr/share/doc/lm_sensors-2.8.1/lm_sensors.init /etc/rc.d/init.d/lm_sensors
If it can't find the file, do find / -name lm_sensors.init, it should look for the file, and give you the directory when found..

Let's start lm_sensors: /etc/init.d/lm_sensors start
Starting up sensors: starting module __i2c-viapro__
starting module __i2c-isa__
starting module __w83781d__
starting module __via686a__
/etc/init.d/lm_sensors: line 61: /usr/local/bin/sensors: No such file or directory
[FAILED]

Well that sucks.., the initscript points to the wrong directory for the sensors binary, open up /etc/init.d/lm_sensors and look for the directive that says: PSENSORS=/usr/local/bin/sensors, and change this to
PSENSORS=/usr/bin/sensors, and try starting it again:
/etc/init.d/lm_sensors start
Starting up sensors: starting module __i2c-viapro__
starting module __i2c-isa__
starting module __w83781d__
starting module __via686a__
[ OK ]

That's better, the lm_sensors package works..

Next step: configuring snmp..

The default config of snmpd is located in /etc/snmp/snmpd.conf, plain to say, this file is a mess of text and what not, I always start with a blank and easy file..
cd /etc/snmp/
mv snmpd.conf snmpd.conf.old

Now open your favorite editor and create something simple like:
rocommunity putapasswordhere
disk / 10000
disk /boot 10000
disk /var 10000
disk /tmp 10000
disk /home 10000

The rocommunity means: read only community, and fill in a password you'll be using to read the data (don't use a very important one like your root pass, since it'll go in plain text over the internet)
The disk entries allow your parititons to be included into SNMP too..

Save the file, and start snmp: /etc/init.d/snmpd restart
Now let's see if you can read the sensor values, type:
snmpwalk localhost -v 1 -c putapasswordhere host.hrSensor

If you did everything right, you should get output like:
HOST-RESOURCES-MIB::hrSensorValue.10 = STRING: 5.040000
HOST-RESOURCES-MIB::hrSensorValue.11 = STRING: 4.720800
HOST-RESOURCES-MIB::hrSensorValue.12 = STRING: 5.241600
HOST-RESOURCES-MIB::hrSensorValue.13 = STRING: 12.084000
HOST-RESOURCES-MIB::hrSensorValue.14 = STRING: 10.792000
HOST-RESOURCES-MIB::hrSensorValue.15 = STRING: 13.186000
HOST-RESOURCES-MIB::hrSensorValue.16 = STRING: -12.317881
HOST-RESOURCES-MIB::hrSensorValue.17 = STRING: -13.192053
HOST-RESOURCES-MIB::hrSensorValue.18 = STRING: -10.728477
HOST-RESOURCES-MIB::hrSensorValue.19 = STRING: -5.146987
HOST-RESOURCES-MIB::hrSensorValue.20 = STRING: -5.237285
HOST-RESOURCES-MIB::hrSensorValue.21 = STRING: -4.740646

That means it works.., that's it.., you have SNMP and lm_sensors running together..

'Right'.., you'll say, 'wtf am I supposed to do with that' ?, the advanced sysadmin will most likely be able to work with all this and integrate it in his/her favorite applications and scripts, A lot of others however will most likely still need a good use for this.. ;-)

A good pointer to start is cacti.net, this is a graphing tool which allows you to create custom graphs using all sorts of (snmp) data

helpful resource I used:
http://people.redhat.com/harald/snmp-lmsensors/HOWTO-SENSORS-SNMPD.html