linux
Yeah, that's probably the best way to do it. Linux can read and write in fat32. It calls fat32 vfat....
Although it can also read and write NTFS, that's still more or less experimental, at least writing in NTFS is still experimental.
That's the way my dual-boot box is setup: NTFS for Windows, Fat32 for sharing between OS's, ext3 for /boot, reiserfs for /root.