I'm not sure the MLK speech applies, since he repeats one word group, and parallelism involves adjacent word groups either complementary or antithetical for rhetorical effect. In that sense, the MLK speech is actually quite literal and declarative.
In contemporary terms, you might explore how lyrics bend pronunciation to make the rhyme (not quite parallelism, but it's at least consistent bunching of modified words playing off each other), how hip-hop lyrics use repetitive structure to reinforce but change meaning as the song progresses (which is parallel in cases where artists use the cadence and/or structure of everyday sayings or slogans - the Wu-Tang Clan is a good example), or, and I'm not joking here, how the way Yoda speaks makes him seems wiser through the consistent disruption of normal word structure (parallelism in the sense that the way he groups words and/or juxtaposes them is for rhythmic and connotative effect). Gil Scott Heron uses parallelism, as do many spoken word poets, though most are on the revolutionary track (e.g. The Revolution Will Not Be Televised is parallel in structure in its rhetoric by grouping the phrases "the revolution will" and "the revolution will not" with the phrases that follow).
