Salt bin Abdullah says that Hazrat Ibn Abbas radiyallahu anhu wore a ring on the right hand, and as far as I can remember he used to say that the Prophet of Allah sallallahu alaihe wasallam also wore it on the right hand (JA)
English reference (JA): Book 12, Hadith 94 (JA)
Arabic reference (JA): Book 13, Hadith 100 (JA)