Watch the Minor Blues Scale online guitar lesson by Jeff McErlain from Blues Guitar Survival Guide - Lead
The Minor Blues scale is just a minor pentatonic scale with an added b5. The b5 is often called the blue note, hence the name of the scale. To most players the pentatonic and blues scale are synonymous because they are so ubiquitous. The blues scale can be traced back to African roots and found its way into the field hollers of slaves and plantation workers in the early 1900's. I highly suggest checking out some of the field recordings of that time on YouTube, that sound is the essence of the blues. On a technical note, the blue note is not usually "sat on" for any long period of time as it causes a dissonance that when used properly adds a great tension. That tension always calls for release.