Nyxem just published a very interesting information. Writing to an NTFS partition was originally activated in the beta versions of Snow Leopard. But this feature was disabled in the final version (probably a rights issue with Microsoft, author of the NTFS file system).
However, there is a way to re-write NTFS on Mac OS X Snow Leopard through the terminal while waiting for someone so small software to enable easy.
Open the terminal located in Applications/Utilities
Then find the UUID of the partition with this command:
Copy the UUID
Create or edit the fstab:
ls /etc/ | grep fstab (to check if the file exists)
cp /etc/fstab~/Desktop/ (to make a copy on the desktop)
Edit the document using the command:
Add the following line:
UUID = uuid_de_la_partition none ntfs rw
or if you do not find the UUID
LABEL = nom_de_la_partition none ntfs rw
Save the file and restart to apply changes.