I wonder if those dialects are on the way to becoming separate languages — Ebonics I think may be going that way. Does it have a grammar (meaning repeatable rules)?
A few rules of ebonics I can think of offhand are the simple use of the infinitive "be" instead of the conjugated forms of "to be" (I be goin' tu dih sto'; you be goin' wit me; he be meetin' up wit us), the absence of apostrophized possessives (den I be goin' roun' Darrell house) and certain situations where the verb is omitted ('cause Darrell mad). The use of "be" plus a gerund can also stand for several past, present or future verb tenses.
One of the more interesting African-American dialects is Gullah, which some scholars say is a language, and others say is a dialect. There is even a translation of the Bible into Gullah.