On piano or synthesizer keyboard, I like the blues scales on D, E, or A to improvise on because the black note falls so conveniently under the fourth finger.

D Blues:

D F G G# A C D

E Blues:

E G A A# B D E

A Blues:

A C D D# E G A

The easiest fingering for the right hand is 1 2 3 4 1 2 3.

I would have to disagree with fricto's assertion that the blues scale is based on the minor scale. It is based on the pentatonic scale, a minor pentatonic scale, to be exact, like the 5 black keys on the piano, with the added tone, the augmented fourth, diminished fifth, or tritone: the G#, A#, and D# in my examples above.

It is also known as the diabolus in musica.