Charlie Parker's improvisational technique was largely based on formulas (or riffs) that he would transpose to fit chord progressions. He would have to do this in order to play as fast and as fluently as he did, even when he was high and this is in no way a criticism of his creativity--he did invent an entire musical language using his riffs as words. A statistical analysis of Parker's formulas can be found in Toward a cognitive analysis of creativity: Improvisation in jazz by Weisberg et. al. and a musical analysis by close reading of the Charlie Parker Omnibook.
Thelonious Monk's contribution was along multiple reinforcing lines. First there were his reharmonizations, which included chords, tone clusters and even microtones--his use of minor seconds was his way of trying to play the note in the crack between the keys. There was his strong rhythm combined with an amazing use of space. And then there was his innovative use of the blues scale to create angular melodies with repeating melodic fragments. To hear just how different his musical sensibilities were, listen to his version of "Tea for Two."
A detailed analysis of Monk's improvisation style can be found in The Musical Language of Thelonious Monk by Eddie S Meadows