ext2resize resizes unmounted ext2 filesystems, either shrinking or growing. I had a situation in which parted would not increase the size of an ext2 filesystem after increasing the size of the partition, but ext2resize did.
There are two other programs in the ext2resize package. ext2online and ext2prepare are for resizing mounted ext2 filesystems. However, ext2online requires a kernel patch.
"Es gibt nichts mehr praktish als theorie" L. Boltzmann