Megavideo Video Downloader will download and save any video on the site for free.
All you need to do is enter the URL of the video you want to download, click the add button to put it in your list of movies to download, and click the start button. Videos are downloaded as FLV files and can be converted and saved as AVI, MPEG, WMV, or FLV files. The utility will also tell you the size of a video file before you begin downloading.
Now, there are many files hosted on Megavideo that have been uploaded illegally, so we of course don't condone downloading or even watching these videos. And if you feel queasy about using software that's designed to get around paying for a legitimate service, you could always pay for a premium account and use the utility anyway. Megavideo Video Downloader allows you to create batch download jobs, which makes it pretty useful even if you're a paying member.