Tea tree oil can work wonders. It soothes, disenfects, deep cleans, and relieves itch. Just apply it straight to the scalp with your fingers, massage it in, wait 30 minutes (or leave it overnight) then shampoo. You could also just add some of the oil to your favorite shampoo. I'm a fan of tea tree! The scent is strong and takes some getting used to tho.
A book I have called Beauty 911, suggests dissolving 15 aspirin in a regular sized bottle of shampoo. Aspirin contains salicylic acid which can help slough off the flakes. I haven't tried this method myself but it sounds worth a shot, since I love how the aspirin mask exfoliates my skin.
A new product I am wanting to try is Neutrogena Triple Moisture for dry scalp. They have a shampoo and conditioner with the active ingredient pyrithione zinc which is the #1 dandruff fighting ingredient. They are designed to be very moisturizing, nurturing, and gentle for the hair. I plan on trying these soon, I'll let you know how they work!