DownloadHelper is a free Firefox extension for downloading videos and images from many sites with minimum effort.

You can save videos from sites where there is no option to download the movie to your hard disk. DownloadHelper works on YouTube, MySpace, Google videos, DailyMotion, Porkolt, iFilm, DreamHost and many others: check here for a longer list of supported sites.

It is also possible to capture all the images from a galery in a single operation.