Best file system to share between Linux, Win & MacOS?

FAT32, should be the choice now. FAT32 (or even FAT16) is really fine unless you need single files >4GB or you need POSIX types of features.

NTFS has somewhat limited read/write support on OS X (using Fuse) and also on Linux, I think.

EXT2 has drivers for both Windows and OS X, though, so if you do need large files or modern features, ext2fs is doable, although you will need to install drivers on every non-Linux box you use with the card.

OSX can read/write HFS, HFS+, FAT16, FAT32, and read NTFS.

如果你想创建一个Linux, Windows, Mac OS 都能识别／读写的硬盘分区。现在看来，FAT32 是个不二选择。但这个分区类型不支持单个文件大于 4Gb 的情况。不过，其它分区类型都不可行，据说有些新的分区格式似乎正在开发。