What shampoo do people with dandruff use?

What shampoo do those of you with dandruff use? I wash my hair twice a day, morning and evening, and I make sure to rinse it thoroughly. Yet, the dandruff just won't go away. There are even some red, inflamed spots on my scalp. It itches, so when I scratch, the dandruff falls onto my clothes. Please share some tips on how you managed to get rid of dandruff!