Answer:
1) Princess Snow White - Snow White and the Seven Dwarfs
2) Cinderella - Cinderella
3) Princess Aurora - Sleeping Beauty
4) Princess Ariel - The Little Mermaid
5) Belle - Beauty and the Beast
6) Princess Jasmine - Aladdin
7) Princess Pocahontas - Pocahontas
8) Mulan - Mulan
9) Princess Tiana - The Princess and the Frog
10) Maid Marian - Robin Hood
11) Nala - The Lion King
12) Megara - Hercules
13) Princess Minnie - Mickey, Donald, Goofy: The Three Musketeers
14) Princesses Mei, Ting-Ting & Su - Mulan ll
15) Alice - Alice in Wonderland
16) Princess Melody - The Little Mermaid II: Return to the Sea
Officially there are only 8 - the other's are "Guest Princesses"
Official Princesses:
Ariel
Mulan
Cinderella
Snow White
Jasmine
Aurora
Belle
Pocahontas