HTTrack - HTTrack is a free (GPL, libre/free software) and easy-to-use offline browser utility.
Syncany - Syncany is an open-source cloud storage and filesharing application.
GNU Wget - GNU Wget is a free software package for retrieving files using HTTP(S) and FTP, the most...
Filestash - Filestash is a modern client for FTP, SFTP, S3, WebDAV, Minio,...
WebCopy - Cyotek WebCopy is a free tool for copying full or partial websites locally onto your harddisk for offline viewing.
Dropbox - Online Sync and File Sharing