To find large directories, use the du command and sort the output.

For example, to output the 10 largest directories in /var, sorted in ascending size order, use the following command:

du -ko /var|sort -n | tail -10

To avoid crossing file system boundaries, that is, to see the directory usage in / but not in the other mounted files systems (/var, /opt, and so on), add the d option to the du command:

du -kod /var|sort -n | tail -10

Finding Large Files

To find large files, use the find command and sort the output.

Example 1: To find all plain files (not block, character, symbolic links, and so on) in a file system larger than 200,000 512-byte blocks (approximately 100 Mbytes) and sort on field 7 (file size) while numerically ignoring leading blanks, do this:

find / -size +200000 -type f -ls | sort -k 7,7 -n

Sourced from: http://wikis.sun.com/display/BigAdmin/Finding+Large+Files+and+Directories+in+the+Solaris+OS