No shampoo
Right, so as of January 1, 2008 I haven't used shampoo in my hair, instead rinsing with a baking soda solution and/or an apple cider vinegar solution more or less as recommended by Natalie. Late in week two of the experiment my hair was almost unbearably waxy and stiff feeling, but after a couple of days it settled into its current state, which is definitely a bit greasier than I'm used to, but the people around me say it looks nice, and it definitely feels very silky. I pretty much used to shampoo every day without fail, so my hair was actually pretty dry I guess, so it's probably actually more close to normal now, and just seems greasy to me.
Some days are definitely greasier-feeling than others, and my main experimenting at this point is to see what things affect my hair depending on its current state. I have a pretty good idea of what the end state of my hair will be when I shampoo it, but very little sense still of what happens if I use baking soda and then vinegar, or just vinegar, or just hot and cold water. I'm probably still using baking soda/washing my hair too frequently, but I want to put something disinfecting-ish in it if I work up a sweat, which is pretty frequently. I generally manage some semblance of BS/AVC one day, nothing or just water the next day, just ACV/water the next day, nothing or just water the day after that, then start over again. Oh and I generally add a drop or two of lavender essential oil to the apple cider vinegar, at first hoping that the scent would stay in my hair, but now just because it smells nice in the shower. It hasn't seemed to have made a difference in the oiliness of my hair. Smell-wise I've received a couple of comments that my hair now smells like me rather than like shampoo. I've interrogated the commenters as to whether "smelling like me" is a nice smell or not, and they've sworn that it's a perfectly nice smell, but I'm not sure if I trust them to answer truthfully or no.
My hair definitely isn't too dry though, well except the very ends but that's because I'm badly in need of a trim.
My scalp broke out a bit more than usual at first, but seems to have mostly subsided. I'm seeing a little more in the way of breakouts on my upper back though, and I'm contemplating the best course of action for that... possibly I'll try doing something with my hair to keep it up while I'm sleeping.