The path I took recently is much like Catkin's suggestion. I created a new partition, formatted it to ext3, did
mount /dev/sda5 /mnt/tmphome ###substitute /dev/sda5 with your actual partition
cp -R /home/* /mnt/tmphome
edited /etc/fstab to mount /dev/sda5 as /home and rebooted. All was well and everything was picked up appropriately. I think you will have to chown -R the new home directories after the reboot.