This is probably obvious to many, but it might be useful anyway: You can use a Windows XP installation in Parallels Desktop VM to get around the read-only limitation of Mac OS X's NTFS file system support.
I had to copy some data from my Mac to an external portable hard disk which is usually used on a Windows machine, and which is formatted using the NTFS filesystem. Mac OS X has read-only NTFS support, so copying from the disk to my Mac is not a problem, but writing is not possible.
Using my Windows XP installation in Parallels VM and its shared folder support, I was able to copy my data from the Mac to the disk. The hard disk was connected via USB and thus visible to Windows in Parallels. It's not as fast as it could be, but at least I was able to transfer my data.
Mac OS X Hints