Suggestions for a free utility to download video from YouTube?

Similarly, a utility to download just the audio from YouTube video?

tanstaafl.

Lots of web sites exist for this purpose. I personally use http://www.clipconverter.cc/

Their user interface is a little weird because the button marked "DOWNLOAD" is highlighted white because that's the default one that's "selected". Since it's not using a checkbox or radio button interface, that might confuse you on first use.

Firefox has an addon called Video DownloadHelper that I've used in the past and works pretty well.

I stopped using Video Download Helper. I seem to recall that it started to look like it was getting spammy/adware-ey/malware-ey. Has it gotten better recently? I'm afraid to try it. :-)

I haven't used it in quite a while. The only thing I noticed was after a browser upgrade, it would go to the Video DownloadHelper homepage.

Other than that, it was pretty minimalistic.

I use a Firefox add-on called "Download YouTube Videos as MP4"

Simply adds a button on the web page under the video and works really well without extra cruft.