More modal trivia:

Note also that two of those 4 are major scales (Ionian, Myxolydian) and two are minor(Aeolian, Dorian) (where the third is flatted and only a half-tone above the second).

And if you reverse the order of the intervals of the more common minor scale, the Aeolian mode (tone, semi, tone, tone, semi, tone, tone) you get the Myxolydian mode (tone, tone, semi, tone, tone, semi, tone).

Reversing the order of the Ionian mode, however, will give you the Phrygian mode, another minor scale--though it is the second note of the scale that is flatted, resulting in the 3rd still being a half-tone lower than in a major scale, even though it is a whole tone above the second. The Phrygian is also popular in other forms of folk music (middle eastern, eastern European, etc.).

Another scale common in folk, Celtic and blues is the pentatonic scale which consists of 5 notes only, leaving out the regular 3rd and 7th notes from the major scale. It avoids the whole major/minor question altogether, as well as whether to flat the 7th or not (whether to go with the Ionic (the 7th being a half-tone lower than the tonic) or Myxolydian (the 7th being flatted and a whole tone lower than the tonic).

There's more scales out there than the 7 ones the Medieval monks made from adapting the original Greek models though: there's the whole tone scale (7 notes, no semi-tones), the diminished scale (9 notes), Enigmatic, Neoploitan, Neoploitan minor, Hungarian minor, and any other combination you'd want to make up, though not all of them sound pretty.