A free utility for NTFS writing on Mac OS X 10.6.5? [duplicate]

Yes. NTFS-3G. You will need to do a bit of hunting to find the free and open source NTFS-3G as opposed to the commercial Tuxera NTFS, which they will quite cheerfully sell you. The latest link at time of writing is on that page under "NTFS-3G for Mac OS X 2010.5.22". I'm not sure if NTFS-3G includes it, but you may also need to install MacFUSE.

If you have macports installed you can install it quickly and freely. It's available.

$ port search ntfs
ntfs-3g @1.5130 (fuse)
    Safe read/write NTFS driver for FUSE

$ sudo port install ntfs-3g

If you want to use other tools you can install ntfsprogs and you will be able to resize, etc. ^^