Use Only 1 Channel of A 2 Channel Amplifier?

Can a person only use one channel of a two-channel amplifier without hurting the amplifier in any way? Do you need to put a "load" (resistor) or something on the one channel not being used? If there is something you can do, does it need to be something to BOTH the output (speaker wire) side and the input side?
I have 3 2-channel amps that I'd like to use in a 5.1 system, but don't want to split them up in case I go to a 6.1 system or something else in the future.
Thanks much, Scott
I asked this same question not too long ago. I am using three channels of a 5 channel Conrad Johnson MF-5600 amp without any problems. I called Conrad Johnson and they said this was perfectly acceptable. There is no need to attach a load to the speaker terminals as long as there in no signal connected to the corresponding input.
For solid state amps, I don't see a problem--I currently use only one channel of each of my Sonogy stereo amps for bass, solely because of space/wiring considerations, and the amps have been fine. Tubes, though, are different, as I believe they need to "see" a load. Perhaps someone more technically oriented than I can chime in.
Just one more 1/2 an amp user. Been doing it for a center speaker,just fine.--Yes it is a ss amp.
Thanks for your responses. Sound's like I'd be OK. The amp is a solid state Llano 200-S. Again, greatly appreciated. Scott