I've tried keepvid and it seems to be working fine... but I think I might try out a couple I found from the threads here
On the YouTube homepage, click on the "Video" tab and in the search box, type in whatever video you are searching for and want to save to your desktop. Click on the actual video that you want and save to the desktop.with the desired video playing, left click on "Save As" and on the drop-down window, look for your desktop option. Once you find the desktop option, click the "Save" button and your video will be saved to your desktop for you to view anytime you want.
If you have Internet Download Manager installed in your computer, you can easily download and save YouTube videos by clicking the "Download Now" button that appears whenever a video is found on any webpage.