The Unknown Lyricist at 2010-01-28 10:05:29:
In animation, there's been a lot. I'm taking it that you want live-action films.

"Roxanne" by Steve Martin comes to mind.
The Film Connoisseur at 2010-01-28 10:36:29:
Black Orpheus -is a modern day retelling of the myth of Orpheus

The Company of Wolves - pretty much retells all of the grim fairy tales in a modern day setting in one horror movie, including Little Red Riding Hood.

Pretty Woman and Maid in Manhattan are both considered moder day retellings of Cinderella.
Adam Cook at 2010-01-28 10:38:11:
Not sure if all these will be relevant to you but...

- The Red Shoes (1948) based on The Red Shoes (obviously)
- The Sweet Hereafter (1997) based on Pied Piper
- Year of the Fish (2007) based on Cinderella
- Criminal Lovers (1999) based on Hansel and Gretel
- AI: Artificial Intelligence (2001) based on Pinocchio
- Some Call it Loving (1973) based on Sleeping Beauty
martinb at 2010-01-28 12:00:50:
COLD MOUNTAIN (2003) is a retelling of the Homeric legend, complete with Sirens etc, according to writer/director Anthony Minghella's DVD commentary.
Darren at 2010-01-28 12:08:52:
Not a film, but you should really look at the comic series Fables, which takes old fairy tale characters and gives them a completely new storyline where they live in a suburb of New York that regular folks don't know about.

It's a very good read that could help inspire you.
Erin at 2010-01-28 12:43:54:
Agreed about 'Fables'.
100% agreed.
The Unknown Lyricist at 2010-01-28 20:41:28:
How about "Enchanted"?
Emily Blake at 2010-01-29 09:47:05:
Roxanne is based on the French play Cyrano de Bergerac.
James at 2010-01-29 12:12:43:
Thanks for all the suggestions guys, helps a ton!
The "Dangerous" Screenwriter at 2010-01-29 16:18:18:
The Cohen Bro.'s "O' Brother Where Art Thou?" is a retelling of Homer's "Odyssey"; though there is some controversy surrounding it's origins, "Avatar" is basically the story of "Pocahontas".