Collectd is a very nice program that runs in the background and gathers statistics about various kind of stuff like  cpu load , disk activity, memory ,fan speed, temperatures, etc, and then puts them all in nice rrd files. It even has a set of scripts to create the graphs. I had only one problem though,  but it was fixable.
Collectd includes sensor.h from lm_sensor package that contains all the functions about your working temperature/fan sensors. It works fine if you only use 1 sensor. But I use 2! 
 it87-isa-0290
Adapter: ISA adapter
CPU core:  +1.78 V  (min =  +1.66 V, max =  +1.84 V)
DDRAM:     +1.31 V  (min =  +1.17 V, max =  +1.33 V)
3v3 I/O:   +3.22 V  (min =  +3.14 V, max =  +3.47 V)
+5V:       +5.09 V  (min =  +4.76 V, max =  +5.26 V)
+12V:     +12.42 V  (min = +11.39 V, max = +12.61 V)
-12V:     -11.47 V  (min =  -7.17 V, max = -16.76 V)
-5V:       -4.03 V  (min =  -2.48 V, max = -10.02 V)
Stdby:     +5.09 V  (min =  +4.76 V, max =  +5.26 V)
CPU Fan:  4166 RPM  (min = 1599 RPM, div = 4)
BOX Fan:  1506 RPM  (min =  897 RPM, div = 8 )
IT87 T°:    +37°C  (low  =   +15°C, high =   +55°C)   sensor = thermistor   
lm90-i2c-0-4c
Adapter: SMBus Via Pro adapter at 5000
LM90 T°:    +47°C  (low  =   +15°C, high =   +60°C)
Athlon T°:
           +53.5°C  (low  = +15.0°C, high = +70.0°C)
LM90 Crit:   +70°C  (hyst =   +60°C)
CPU Crit:    +80°C  (hyst =   +70°C)                   
As you can see I use both it87 and lm90 to get correct results. Collectd creates its rrd databases inside /var/lib/collectd. The sensor rrd file it creates are in the form: 
sensors-fan1.rrd
sensors-fan2.rrd
sensors-fan3.rrd
sensors-temp1.rrd
sensors-temp2.rrd
sensors-temp3.rrd
That means it can’t distinguish the different chipsets and overwrites the values if you have 2 chipsets. What I did was patch collectd to rename the rrd files in order to include the sensor name as well. I now have:
sensors-it87-fan1.rrd
sensors-it87-fan2.rrd
sensors-it87-fan3.rrd
sensors-it87-temp1.rrd
sensors-it87-temp2.rrd
sensors-it87-temp3.rrd
sensors-lm90-temp1.rrd
sensors-lm90-temp2.rrd
The patch is here: Collectd-multi-sensor.patch.gz
Just apply the patch inside the src dir , recompile and install.
I am in doubt whether I should contact the author or not about this simple patch…anyway…If you use collectd and have more than 1 sensor running…tell me if it works for you…
cheers!