How to locate small file consumption creep

[Josef Lowder]

How can I locate what seems to be a small file consumption
"creep" on my system.  In one 10-gig partition, I have about 1.1 gig
of free space available, but I've noticed that some of this space
seems to go away overnight when nothing is running.

For example, last night 'df' showed this:
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda2             9.9G  2.7G  6.7G  29% /
/dev/hda1              76M  5.3M   67M   8% /boot
/dev/hda3             9.9G  8.8G  1.1G  90% /home
/dev/hda7             9.9G  7.3G  2.1G  78% /mnt/hda7

And this morning, 'df' showed this:
Filesystem            Size  Used Avail Use% Mounted on
/dev/hda2             9.9G  2.7G  6.7G  29% /
/dev/hda1              76M  5.3M   67M   8% /boot
/dev/hda3             9.9G  9.0G  951M  91% /home
/dev/hda7             9.9G  7.3G  2.1G  78% /mnt/hda7

So what could account for the loss of file space from
1.1G to 951M overnight with nothing running
and how could I search my system to find an answer?