Sleep issues

Yes, I mean the computer. In this case, my 15" MBP, Mac OS X 10.6.6. Here's the issue: Before I go to bed, I put the laptop in sleep mode by using the shortcut (command-option-eject), wait for the fan to shut down (I use smcFanControl so I hear it shut off), and see the white indicator light begin fading, and then close the laptop. However, within 20-30 minutes, I'll hear the fan randomly start up again and run for 20-60 seconds before it shuts off not to be heard from again until I wake it up the next day. Any thoughts?

Welcome to the Mac Forums.

Does the machine come out of sleep mode when the fan ramps up? Also, it's not a good idea to use SmcFanControl to control the speed of your fan. The machine has been designed by Apple engineers to respond to temperature changes thru sensors which in turn control the fan. There is no need to circumvent that. Use SmcFanControl as a monitor only is OK.
Turn off Smc and see if that resolves the problem. If it doesn't, there is something else which is going on that causes the fan to ramp up.

The computer waking from sleep mode is actually what causes the fan to ramp up. Basically it wakes up (I know because my external USB hub lights up as soon as it wakes), and then a couple seconds later the fan ramps up. My reasoning for having the smcFanControl in the first place is that, with the way I use it, I needed to be more in control of the temperature. Usually having the fan at the higher speeds keeps the CPU 15-25 degrees (Celsius) cooler than without it. I had an external (USB powered) fan, but that wasn't very effective, and was much louder than I liked. It's now a laptop stand to keep the system elevated for more comfort.

For what it's worth, it doesn't happen every day (for example it didn't happen last night); If it persists I'll probably look into turning it off before I'm done for the night.