Originally Posted By: PeterGannon
In the key of C, in addition to the chords in C, the dominant 7th approaches to each of the chords are allowed, and seen often. This brings in all these chords, G7,A7,B7,C7,D7,E7,F#7. Of those chords these ones are used very commonly C7, D7, A7, E7, G7
G7 -> C
A7 -> Dm
B7-> Em
C7 -> F
D7-> G
E7-> Am
F#7-> Bdim

Short demo of just these chord pairs:

https://soundcloud.com/mark_hayes/dominants