This tool can be installed easily using the package name ncdu:
$ sudo apt-get install ncdu
To find the disk usage at the current directory, just invoke ncdu. The space occupied by the current directory is shown at the bottom bar as Total disk usage. The main window shows a list of the subdirectories and the space they occupy. Use the j-k or up-down keys to move along this list and press Enter to analyze the disk usage of any subdirectory. This makes it easy to drill down to find the directory that is hogging disk space. To quit ncdu, press q.
Tried with: ncdu 1.8 and Ubuntu 12.04 LTS