Life is a constant war against the limited size of backup media. Here is my next weapon in the fight: dusub. Save a du listing today, then find out tomorrow or next week what's been growing: 
dusub olddu newdu
or 
du … | dusub olddu
Positive numbers in the output represent an item that grew since olddu; negative numbers represent a decrease in size since olddu.

Version 2 knows about "du -h"-style listings.

dusub is useful with sorttop: 

du … | dusub olddu | sorttop

Files currently attached to this page:

dusub-v2.py2.4kB
dusub.py1.4kB