A much more stable NTFS layer for Mac however is Paragon NTFS, especially if you’re a lion user.
http://www.paragon-software.com/home/ntfs-mac/
Not free, although a 10 day trial is available, and it’s less prone to data corruption than Joe S’s suggestion since it’s kept updated, whereas NTFS-3G I believe hasn’t been refreshed since Dec 2010 which pre-dates Lion. And it doesn’t require the second MacFuse layer.
