Megara
Even though Meg admits that she is a damsel in distress, she also says that she can handle her own problems. Meg is also one of the few Disney characters (male or female) that sacrifices herself to save someone else. Meg also proves that your first love is not always "the one" as seen when her first boyfriend leaves her for someone else. Meg is a very underrated Disney character despite marrying a god, but is also seen as being not for children because she is depicted as someone who is comfortable with her sexuality.
Esmeralda
Esmeralda is another severely underrated Disney character, but is still very powerful in her own right. She stands up to perhaps one of the most terrifying Disney villains and to racism itself. Esmeralda also befriends Quasimodo, whom everyone else in Paris is afraid of because of the rumors and his disabilities. Esmeralda is also seen by some as a "not for children" Disney character because of how she challenges authority and and how she is depicted.
Belle
With the new Beauty and the Beast movie coming out next year, everyone is reminded of why they love Belle. She's caring of her family, yet courageous in front of the Beast. She loves to read and learn and will not stand for Gaston's old-fashioned views of how women should not be thinking. Belle proves that any girl can be can be smart and educated and still get their happily ever after. Even though Belle may be in the Disney spotlight a lot, she's still a heavily empowered female character who proves to be way ahead of her time. Emma Watson is a great casting choice for Belle.
Tiana
Tiana is a workaholic; you'd never think to see that in a Disney princess. She never loses sight of her dream to open a restaurant, a dream she and her late father both shared. It can be easy to dismiss Tiana as another Disney princess in a fancy, poofy dress, but Tiana is empowered because she does not let people walk over her. Even when her prince refuses to work in the beginning and claims that she is "just a waitress," Tiana always proves that she is more than what she seems.
Mulan
Before Elsa stayed single and before Merida shot for her own fate, there was Mulan. Mulan was the original feminist princess who proved that she didn't need a man to succeed. Mulan not only took her father's place as a soldier, but also took down the Hun army leader by herself. It is not question that Mulan is the ultimate Disney princess. She's tough, enduring, and comfortable in her own skin. Mulan also relates to the average girl by having her less than graceful moments, but still having a mind of her own.