Folx is a free download manager compatible with the HTTP, HTTPS and FTP web protocols. In addition, it allows for multi-threaded downloads, which allows you to download files more quickly because it divides the downloads into various parts.
It has a number of interesting characteristics, such as automatically re-starting downloads if you lose your internet connection, a download programmer which allows you to set up a personalized schedule to download files, and a download organizer based on tags and compatible with Spotlight.
Folx also offers the possibility of downloading complete directories from a FTP, which keeps you from having to download files one-by-one. It allows you to restrict the bandwidth that the program uses and it has browser extensions that allow you to catch download links.