I havent cosplayed any Disney characters (YET!) but some not-princess ones I can think of are Jane from Peter Pan 2, Pocahontas, Cinderellas sisters and mother, Lilo from Lilo and Stitch, and any of Ariels sisters (who are technically princesses but not major ones so I hope thats fine).
Cosplays in progress
Pikachu [Pokemon]- Anime Boston 2010
Belle [Disney's Beauty and the Beast]
Hungary [Axis Powers Hetalia]
Tina Belcher [Bob's Burgers]
Hinata Hyuga [Naruto Shippuden]
Rin Nohara [Naruto Shippuden]