My Linux computer will read any disk or storage device with just about any file system on it. Notably, ext3, ext2, HFS, HFS+, NTFS, FAT32.
My Mac will read HFS, HFS+, and FAT32 for sure. It can probably read the others, but I've never tried it.
Windows can only read NTFS and FAT32.
Now, from a technocratically competitive point of view, this makes sense. Microsoft doesn't want you messing with these other file systems. While Linux and Apple have to make these small concessions to the dominant power.
But it sucks all the same. I personally consider this level of non-interoperability one of the worst things about Windows. I should be able to plug my HFS+ iPod into any computer anywhere and download/upload songs. But no, Windows doesn't allow it. It's not like it's hard or anything - Linux seems to do a pretty good job of handling HFS+ and recognizing what it should do with an iPod. But Microsoft just cannot be bothered to do something that useful. Whores.