Most relatively new Linux users might have used the
wget command a few times while installing packages or grabbing specific files, but the little command word can be a pretty powerful tool. The FOSSwire open source blog points out how you can use wget to mirror a website, either one page at a time or with all the internal links available for offline browsing. As noted, however, grabbing large, multi-page sites can be a serious drain on bandwith (both yours and the site's), so adding a delay option is both considerate and wise. Hit the link for details on using wget for offline website access.