How hard would it be to make a preamp for a pair of headphones, for sitting around with whilst I'm babysitting or whatever? I'm thinking just a piece of pine with holes for a high/low and gain knob that goes straight to a pair iPod style headphones?

"I don't have an instrument, I don't have a great voice, I just have some nice clothes maybe." paul rutherford
just buy a 10 watt amp and a 1/4" to 1/8" adapter.... its what i do
Some guitar pedals also act as pre-amps , and you can buy headphones with a normal 1/4" guitar jack cheaply from almost anywhere.

Apart from that vox makes special pre-amps with effects built in for headphones.
About 40$ a pop.

Edit: RHCP beat me to it.
Those vox things are great... They dont sound the best but it gets the job done
flintazra wrote:

I think the next person to shoot up a school should list Jonas brothers and Hannah Montana as his favorite "musicians."