A friend on Facebook posted a link to this explanation of the Lydian scale, and it's very well done. With the simple graphics and musical examples it does a great job of getting across the feel of a scale that's neither major or minor, the two scales we sort of mostly settled into around the time equal temperament came in during the 18th century.
Since at least Plato, there's been the feeling that different modes elicit different mental/emotional states in people. Before equal temperament came in (which makes it much easier to modulate from key to key) the different modes had a stronger flavor due to the more pure tunings used (e.g. C# and Db weren't the same pitch as they are today). The examples here, though, show that they still have a feeling different from either major or minor.