Ever needed to take interesting websites, online books, websites under development etc. with you? Perhaps even to places with flaky internet connection? If you so, you should consider download the websites and take them with you, e.g. on USB sticks or other portable media.
Downloading a website is also useful if you need to present website development work to clients or backup some information website for later offline browsing.
With website download tools, you should make sure they can use multiple connections, support include and exclude filters for crawl and download, can follow all kinds of references including redirects, frames, javascripts and images, supports automated download of websites at times convenient to you, e.g. at night etc. More than anything, you should also make sure to test them on a variety of websites.
One website downloader tool that supports all of above, and has a trial period where you can test everything, is A1 Website Download - http://www.microsystools.com/products/website-download/ For more alternatives, try search Google for search phrases such as "website download", "website downloader", "download websites" and similar. You can also try check http://www.download.com for more options.