I always assumed that I couldn't give my DS peanut butter until he was 5 (I remember reading that somewhere) but I have just got some information which says that as long as there is no history of allergy in the family (which there isn't) then smooth peanut butter is fine from 6 months old.
Am a bit surprised by this so thought I would check - it would good if I could as I often have peanut butter on toast for lunch and it would be handy if I could give my DS a bit to nibble on at the same time.