Movgrab is a command-line movie downloader for sites like YouTube. It has no dependencies; everything that's needed should be there in the tar.gz package. Movgrab can connect through an HTTP proxy, can output the download to stdout for piping into another program, and can fork into the background to free up the console. When forked into the background, its progress can still be seen in a ps list.
Elmedia Player PRO makes it easy to download videos from online sources such as YouTube, Vimeo, DailyMotion, Metacafe, and many others. Using it is just a matter of entering the link to the page with your desired video in Elmedia Player and choosing the content you want to download from the list. When you are downloading SWF files, you are given the option to preview all external resources used by the SWF animation. You can download them along with the SWF file if you wish, or even download just the external resources without the initial SWF. Other features include full-screen mode, "Always on top" mode, the ability to make screenshots of your favorite movie moments, and the ability to convert the whole movie into a series of images.
Jaksta is an easy way to download and convert video, audio, and MP3s from the Web to your Mac. Just open Jaksta, then play a video or song in your browser, and Jaksta saves a copy to your Mac's hard disk, or converts it to several popular device formats. It works with thousands of sites, including YouTube and Facebook, as well as popular music sites.
getxbook is a collection of tools to download books from websites. There are tools to download from Google Books' "book preview", Amazon's "look inside the book", and Barnes and Noble's "book viewer". There is an optional GUI written in Tcl/Tk, and some shell scripts using OCR to create plain text or searchable PDFs and DjVu files from the downloaded books.