HTTrack is a free (GPL, libre/free software) and easy-to-use offline browser utility.

MetaProducts Offline Explorer is a Windows XP/Vista/7/8/10 program that allows you to download an unlimited number of your favorite Web and FTP sites.

WebCopy is a free tool for copying full or partial websites locally onto your harddisk for offline viewing.

Teleport Pro is an offline browsing webspider.