Sync with a Directory Listing of Web Server

wget is a great tool.

Use wget -m http://somesite.com/directory

-m
--mirror
    Turn on options suitable for mirroring.  This option turns on
    recursion and time-stamping, sets infinite recursion depth and
    keeps FTP directory listings.  It is currently equivalent to 
    -r -N -l inf --no-remove-listing.

Like rsync, but use zsync to get from an httpd server.