Little Bean knows all the letters and their sounds, and is doing a bit of reading (CVC words only). However, I find that many times he gets the sounds for d, b, and p mixed up, which I know is a common problem. In order to work on this a little bit, we tried the following activity.
I pulled out three letter cards (d, b, and p, of course) and then gathered several toys that began with these three letters. I asked him to arrange the toys underneath the appropriate letter. He has no problem telling me what the initial sound is in any (or most any) word. However, this activity was extremely difficult for him, because he got confused on which letter was which visually. He knew diaper began with the /d/ sound, but couldn't remember which letter represented that sound. Once he had at least one item under each letter, he was able to complete the activity because he would just compare the sound of the object in question with the sounds of each of the objects under the different letters. He was able to complete the activity with some help from me, but I need to think of some more ideas to help with visual discrimination.