If you want really eco-friendly, wash them all by hand using becky's eco-chips while bending over a stream.
Barring that, washing in cold water actually produces less wear and tear on your clothes than hot water does (ie less fading and/or shrinkage). Also, running an extra spin cycle cuts down your drying time in the dryer.

The extra spin cycle is a big hit in houses like mine where the dryer vents the heated moist air through a little tube up the fecking wall and into the attic.....which means to dry a load, I have to run the dryer 3 to 4 times. But that added spin cycle cuts my drying time down to 1-2 cycles.

Edit: I doubt any of these are eco-friendly, but they are supposed to be cheaper than purchasing acutal laundry soap:
tipnut.com/10-homemade-laundry-soap-detergent-recipes/
( flirting with badgers What? It sounded good at the time., Fri 1 May 2009, 4:05, Reply)