I haven't used shampoo for a few years now - I just use bicarb and some water. I used to follow with just a plain apple cider vinegar rinse, but after reading a few skincare and herbal books I decided to try making a herbal vinegar rinse. This month it's a mix of mullein and chamomile - supposedly good for blonde hair (according to James Wong from Grow your own drugs). It's very easy - put vinegar and the herbs (fresh or dried) in a jar, and leave in a sunny spot for 2 weeks. Shake/stir gently every few days. Drain. I use 1 part vinegar to 3 parts water in an old shampoo bottle as a rinse.
The added bonus is that bicarb and ACV are VERY cheap compared to shampoo and conditioner. My scalp is in much better condition since I started this regime (less itchy and flaky) and my hair looks and feels good. Once every 4-6 weeks I do a "hair mask" with olive oil or jojoba if I'm feeling decadent. Just massage it in, leave for 2 hours under a showercap/cling film then wash out. The jojoba in particular leaves my hair super soft and shiny.