Ubuntu Feisty Fawn (the development codename) has a fairly easy way to enable write mode on NTFS partitions. Writing on such partition is safe since release 1.0 of NTFS-3G, and it is included in Ubuntu Feisty’s Universe repository.
To use it, one should enable the Universe repository and install ntfs-3g package (see Ubuntu documentation about installing software) and that’s almost it.
You can now either update manually your partition configuration file (/etc/fstab) to use ntfs-3g driver instead of the default ntfs. Or you could use the ntfs-config package which does the trick taking care for you about the local settings or external hard drive. Who said Linux was not easy?