What's the easiest way to resize one's root partition?

I put a new 320 gig hard disk in a RHEL3 server and cloned the old 20 gig disk. Unfortunately, the partitions are all the same size that they were before. Is parted the right (and easiest?) tool to use for an ext3 partition? Do I need to boot from a livecd or something of the sort to resize the root partition?

Thanks