Harmonic Minor - If your playing in the key of A minor and the chord progression contains a dominant7 chord built on the 5th scale degree (E7) you are in Harmonic minor.

Blues Scale - this scale is a little different then your major/minor/modal scales in that chords are not constructed from this scale. Remember the western/european major/minor system is thousands of years old, but the Blues is only a couple of hundred years old, so traditional theory does adhere to the blues scale phenomenon.

Traditionally this scale was constructed to be used over a 1 4 5 progression of dominants. Ex; key of A {A7 D7 E7}. However you will find that this scale will work over both major and minor progressions (A D E) or (A- D- E-) or (A- D- E7).
The historical importance of this scale was the usage of minor based melodies overtop of major sounding chord progressions.