Yep, mkfs.hfsplus does it.
dd if=/dev/zero of=/tmp/foo.dmg bs=1M count=64
mkfs.hfsplus -v ThisIsFoo /tmp/foo.dmg
This creates a dmg file (in this case 64M) that can be mounted on a mac. It can also be mounted on linux, with something like
mount -o loop /tmp/foo.dmg /mnt/foo
after wich you just copy the content you want to it (in /mnt/foo). Unmount it, and the dmg can be copied over to a mac and mounted there.