Is File Vault 2 whole disk encryption or whole partition encryption?

Question

Can I use File Vault to encrypt only some of the partitions on my disk (so that I can still have unencrypted and Windows partitions on the same disk), or does File Vault encrypt the whole disk so that you cannot even get to the partition table without decrypting it?

And if not, is there any support for reading File Vault disks on Windows, Linux, or, for that matter, Snow Leopard ?