Other Swan Stories

"The Wild Swans"  by Hans Christian Andersen (1838)
In this tale, a king has 12 children (11 sons and one daughter); he marries an evil witch who turns his sons into swans and banishes his daughter Elisa. Elisa knits shirts from nettles, a project that will eventually aid in the restoration of her brothers, but is not allowed to speak a single word during this time. She is accused of being a witch and sentenced to be burned at the stake, but her brothers, as swans, come to her rescue just in time. The swans don the shirts, return to their human form, and explain Elisa's tale, causing her to be freed.
"The Six Swans" Collected by the Brothers Grimm
In this story, a king's six sons are turned into swans by their stepmother. They revert to human form for 15 minutes each day. As in the previous tale, their sister, the princess, is not allowed to speak a single word, and she makes shirts for her brothers, this time out of starwort. She marries another king, but this king's evil mother plots to have her burned at the stake. Just in time, the princess' brothers arrive, put on the shirts, become humans again, and rescue their sister. The king's mother is killed instead.
A Variety of "Swan Maiden" Tales
Link to texts of several such tales: http://www.pitt.edu/~dash/swan.html
These tales generally involve women, rather than men, taking the form of swans; in many such tales, a hunter, sometimes a king, is attracted to such a swan, and he often ends up marrying her.
The Swan Princess, Disney Film
Information page, including movie trailers: http://www.imdb.com/title/tt0111333/
In this film, Princess Odette is cursed by the evil Lord Rothbart so that she is human only when the moonlight is on the lake; at all other times she assumes the form of a swan. Prince Derek loves Odette and attempts to rescue her; his attempts are initially thwarted and he is deceived by Rothbart's assistant who is put under a spell to look like Odette. Eventually, however, he discovers the truth and kills Rothbart, thus lifting the curse from Odette. Prince Derek and Princess Odette finally wed.
"The Princess Swan," the tale by Mary Virginia Boone, differs from these other tales in many respects. The princess is initially a swan who is transformed into a human, rather than the other way around. She is not forced to maintain silence, nor does she create shirts from plants. However, this story is similar to some of these other tales in that a transformation does occur between human form and swan form, an evil enchanter or enchantress is involved, and, generally, the woman/swan has a happy ending with her lover. The tale is particularly similar to The Swan Princess, the film which served as the inspiration for the fairy tale. The title of the story is clearly an inverted version of the movie's title, reflecting the original transformation from swan to princess rather than from princess to swan. A frog aids the princess in both versions, with Jean-Bob aiding Odette in The Swan Princess and the nameless frog restoring the princess to swan form in "The Princess Swan."