Although I still don't have an iPod, I use the free iTunes program quite a lot to play music while I work. But I've been a bit troubled by its apparent tendency to favour certain songs over others. I realize this is probably just the luck of the draw, but I'd prefer to avoid it, and now I can.
I found a tip somewhere on the Web that seems so obvious once it's pointed out. Just set up a smart playlist that excludes any songs played recently. I chose to exclude any songs played in the last month.