Download YouTube videos
If you want to d/l a YouTube video and do it quickly and easily, do this:
Use Firefox.
Bring up your add-ons window under "Tools." Do a search and when you find it, install the "UnPlug" add-on and restart Firefox.
Go to the page that has the video you want and click the UnPlug icon on your toolbar (if you set it to appear that way in your preferences) or if it's not on your toolbar, go to Tools>UnPlug in your Firefox menu bar and it will do its magic and give you a button to download the video to your HD.
If you care about security, don't ever watch any Flash embedded videos through your browser. Download everything to your hard drive and play them. It's a double bonus that they'll play smoothly as well.