OpenStax
Open Stax: Catherine Schmidt Jones: Scales That Aren't Major or Minor
As the title suggests, this site defines and gives examples of various other types of scales including chromatic, whole tone, blues scales and more.
Open Curriculum
Open Curriculum: Scales That Are Not Major or Minor
To explain the various musical scales that cannot be classified as major or minor such as chromatic, whole-tone, pentatonic, blues, and scales from non-Western music