KeepVid is a website that allows you to download videos from YouTube, Vimeo and other popular streaming video sites. Simply type in the URL of the video in the blue box and click on the Download button (also in the blue box). You can also optionally search for a keyword and then click on the video you wish to download. You will then be prompted to run the KeepVid Java applet. Click on the Run button to continue. You should then see the video you are trying to download and several download options below it such as Download as FLV or Download as MP4.
You can also optionally download just the audio by clicking on the Download MP3 option. This will open up a new window or tab in your browser and ask you to run the SnipMP3 Java applet. Again, click on the Run button to continue. Click on the Download MP3 link below the video to download the audio in MP3 format. You can then open the MP3 in Audacity and slow down the audio if you choose to do so.
Check it out here: http://keepvid.com/