there are loads of utilities out there to allow r/w to NTFS, like NTFS 3G, Paragon NTFS etc.
there are also guides on how to enable native r/w to NTFS using a few terminal tricks.
if your working with an external drive or thumb drive reformat them to exFAT (FAT64), it has native r/w in both OS X and faildows, but remember to use the MBR partition scheme.
google and ye shall find!