hard drive - Disk usage per user in Linux / Unix

I need to find out how much disk space is being occupied by each user on the network. I am aware of df and du commands: I could list the entire filesystem and AWK the output, but I wonder if there is a more standard command.

The output I am looking for is:

usr1  xMb
usr2  yMb
[...]
Total zMb

Any ideas?

Thanks!

PS. Red Hat Linux EE