Source: http://superuser.com/questions/9847/linux-utility-for-finding-the-largest-files-directories

To find the largest 10 files (linux/bash):
find . -type f -print0 | xargs -0 du | sort -n | tail -10 | cut -f2 | xargs -I{} du -sh {}

To find the largest 10 directories:
find . -type d -print0 | xargs -0 du | sort -n | tail -10 | cut -f2 | xargs -I{} du -sh {}

To find  the largest 10 directories (centos)
du -a /var | sort -n -r | head -n 10

Human-readable format
cd /path/to/some/where
du -hsx * | sort -rh | head -10

From Mohan
du -h . --max-depth=2 | sort -hr | sed -e 's/$/|/g'

Find top 5 largest log files

du -ha /var/log/* | sort -rh | head -n 5
-h = Print sizes in human readable format (e.g., 10MB)
-a = Displays all files and folders
-S = Do not include size of subdirectories
-s = Display only a total for each argument
-c = Displays total amount of space used
-k = Displays the file size in kilobytes
-m = Displays the file size in megabytes

sort = sort lines of text files
-n = Compare according to string numerical value
-r = Reverse the result of comparisons
-h = Compare human readable numbers (e.g., 2K, 1G)