wget -r -np -nH --cut-dirs=3 -R index.html http://hostname/aaa/bbb/ccc/ddd/

Explanation:

• It will download all files and subfolders in ddd directory
• -r : recursively
• -np : not going to upper directories, like ccc/…
• -nH : not saving files to hostname folder
• --cut-dirs=3 : but saving it to ddd by omitting first 3 folders aaa, bbb, ccc
• -R index.html : excluding index.html files

Reference: http://bmwieczorek.wordpress.com/2008/10/01/wget-recursively-download-all-files-from-certain-directory-listed-by-apache/