It seems the / partition is getting full and is probably causing some crashes we've been experiencing. Does anyone have any idea of what might be taking up the space? I wouldn't even know where to being to look....

[admin /]$ df
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/hda1 743466 723784 19682 97% /
/dev/hda3 198601 96480 102121 49% /var
/dev/hda4 17671528 1803461 15868067 10% /home