There are lots of apps that I find fun or useful. Pocket is an app that is both.
Also available as a web app, you can save webpages, images, and videos for offline reading/viewing. Mark items as read and they disappear from view – but if there is an internet connection, you can retrieve archived items. Pocketed items can be tagged into categories for easy retrieval as well.
I find this app incredibly useful when reading long articles, or when I might want to do some bus reading. Articles can be viewed as they would be online, or as a PDF-like “readable”view.
An account is required, but you can export your pocketed information, and with very few clicks clear your data and delete your account.