A port of the original iotop to C with additional features. Acts like top but for disk I/O. Good for keeping an eye on what's bogging your disk array down.
You can add a capability so that you don't need to be root to run it: sudo setcap 'cap_net_admin+eip' /path/to/iotop
Here's my command line: iotop -o -2 -6 -8
In the AUR as iotop-c.