So now that I have mastered the major scale....

Very simply, to get a purely major sound. It would be best to play a C major scale, or even a C major pentatonic scale over a C major scale.

For minor, there are a few more options. But for C minor, the C minor and C minor pentatonic would work as well (there are actually 3 minor scales so there are more options).

But I once read, I think on another post here, that over a major scale, that a minor pentatonic would work better, or a blues scale (which is basically similar), and you can also play like an A minor scale, or something like that. I don't really know that's why I am asking. Did I read this wrong?? Basically what I am asking is what are all the scales that would work in a major key.

Michhill8, there's not really a simple answer, which may be why you haven't gotten many replies.

(Well, okay, like Steve-O said, one possible simple answer would be to play Cmaj or Cmaj pentatonic over a chord progression in C ... but I think you're looking for the "how" and "why" as much as the "what.")

You're getting deep into music theory here, and it's way beyond me to answer, but I think this article from Darrin Koltow has much of the information you are looking for:
http://www.maximummusician.com/GuitarImprovising.htm

He covers some of the scales you can play over a chord progression; of course, you could also use arpeggios.

Also keep in mind that Amin pentatonic is the same as Cmaj pentatonic (A being the 6th note of the Cmaj scale) - I think this is the minor scale you are thinking of.

hey thanks slejhammer