Two of the most effective tools I've found for keeping videos embedded in Web pages are the Free FLV Converter and RealPlayer. Yes, that RealPlayer.
RealPlayer version 11 beta comes with the ability to download embedded vids from the Internet, but it saves them as Flash video files, either in FLV or SWF formats. Neither one is particularly useful if you then want to burn the vid to a DVD or rip it to a portable device. The Free FLV Converter is a simple app that cures that problem by quickly and effectively changing it to AVI format for DVDs or one of several portable formats compatible with iPods, iPhones, PSPs, and others.
To get going, install both programs and point your Web browser to YouTube or some other video-sharing site. As you mouse over a video, you'll notice a pop-up in the upper-right corner with the RealPlayer icon that reads Download This Video. Clicking on the text to download the vid or on the arrow next to it to changes the preferences, including the name and location that the video gets saved under.
The RealPlayer download manager will then open. After the video has been downloaded, you can open the folder that it's in directly from the manager. I do this just so I know where the video is. From there, open the Free FLV Converter and hit the third tab, Conversion from FLV. Take note that the second tab, Tube Downloader, does download embedded videos, but it doesn't support all embeds.
Hitting the Conversion tab will automatically open a file browser so you can choose your victim. From there, a conversion window opens up and you can change the basics such as settings, including output format, quality, and destination directory, as well as more advanced options like the codec, aspect ratio, and the framerate. Tap Convert at the bottom of the window when you're ready, and the Free FLV Converter works smoothly and without interfering with other programs.
Free FLV Converter does have one annoyance: When you install it, be sure to opt out of the Dealio toolbar. Still, it's definitely a minor drawback when you consider the benefits of watching videos from the Internet when and where you want to.