FAT is the most compatible filesystem. Downsides include limited file permissions, and a 4GB filesize limit. Also, Windows refuses to create a FAT filesystem larger than 32GB. But other tools will.
NTFS (= Windows filesystem) has poorer cross platform support than FAT, but it has fewer limitations than FAT. I think you should be able to read NTFS in OSX without additional software, so it could work for you if you don't need write access. And it should be readable and writable in Linux.
As for partitioning, I dunno. Does a hackintosh require two partitions for itself?