The Unicode Standard v5.2 has just been published, and includes revisions to the table of dual-joining characters that clarify the behaviour of two extended Arabic characters: the Farsi (Persian) yeh U+06CC, and the Jawi (Malay) nya U+06BD. Note that this change does not involve new characters, but only clarification of how these existing characters should be displayed in various joining conditions. This clarification is necessary, because these characters do not inherit dot positioning across the various joining forms. For details, see the table on page 16 of this PDF:
Note also joining class for the Burushaski yeh barree letters U+077A and U+077B, which was added in Unicode v5.1.