Find Large Files

find /var/www -type f -size +10240k -exec ls -lh {} \; | awk '{ print $8 ": " $5 }'

Find top 50 largest directories

du -x /* -d5 -hx * | sort -rh | head -50

Find the size of a directory

du -sh /path/to/directory

Probably my favorite

for i in G M K; do du -ah | grep ^[0-9\.]*$i | sort -nr -k 1; done | head -n 110