Unfortunately, as ZFS is licensed under Sun's CDDL (Common Development and Distribution License) instead of the GNU GPLv2 or GPLv3, this file-system hasn't been supported within the Linux kernel. There is a ZFS implementation for FUSE, but that's not too great. Recently though on the Linux Kernel Mailing List there has been a discussion about bringing read-only ZFS file-system support to Linux.
Sun has made available minimal ZFS file-system support for the GRUB boot-loader under the GNU GPLv2 license. However, this level of support really is minimal, but may be enough for basic read-only support within Linux. However, key kernel developers have stated this wouldn't work and still would be in violation of Sun's patents covering ZFS. Our friends over at Kernel Trap have covered this story.
As many of you may recall and for what it's worth, Linus Torvalds had met with Jeff Bonwick back in May. Jeff is the CTO of Storage Technologies at Sun. On Jeff's Sun blog were several photographs of the two along with a few interesting statements... Several had speculated that this talk was about ZFS and Linux, but no formal explanation of this meeting or the results have yet to be publicized.