How to resize an ext4 encrypted home partition?
Boot Ubuntu from the LiveCD (or a USB-key) and run gparted. In the top-right you can select your harddisk. When it is selected you can just right-click on the partition and chose resize.
eCryptfs encrypts single files and not the whole partition. So can safely resize the partition as you like. Remember that you should have backups of your things!
eCryptfs doesn't have on-disk partitions. To be safe, be sure that you've unmounted your eCryptfs-encrypted home directory and then follow the usual steps to resize the ext4 filesystem.