Attached Link: Customize Firefox

Mozilla has many FREE add-ons for their FREE web browser Firefox available from their site that can download YouTube videos. I use a Firefox add-on called "Flash and Video Download". It's ok and works most of the time but there are many other add-ons too you can try from Mozilla Firefox website. My cousin uses the Firefox add-on called "1-Click YouTube Video Download". It's ok too.

I also strongly recommend getting the Firefox add-on "Download Statusbar" at the same time to see the progress of your download. And of coarse the Firefox add-on "Adblock Plus"; the name speaks for itself.
But be cautious - the more Firefox add-ons you apply then the more unstable your browser will get. Keep it to only what you need.

Also Online-Convert.com can download and convert FREE just about anything online without installing a program. Just give them the link to the YouTube video you want to download and/or convert and their site will do it and download it to your PC.

I am not sure if there is any privacy issue with their conversion service. But just in case be careful what links you are trying to get.

Online-Convert and the Firefox add-ons are ok but just don't expect fantastic results.

Most YouTube videos are in FLV format so you will need an FLV player. Well VLC Player from www.videolan.org is a FREE player of almost any type of video format.

Enjoy.

Good to point this out!  One I will add, that if you get downloadhelper for firefox it will download most video from most sites and if you want it to, can convert it as well.  For youtube its menu will bring up all the various resolutions so you can pick which one you want to grab.  It is free as well. 

And if you use Safari, it's as easy as using the activity window and double clicking on the desired file.

Quote - Good to point this out!  One I will add, that if you get downloadhelper for firefox it will download most video from most sites and if you want it to, can convert it as well.  For youtube its menu will bring up all the various resolutions so you can pick which one you want to grab.  It is free as well. 

Hi Xerxes0002, the ability to choose the resolution sounds great. I typed in "downloadhelper"in the search box at Firefox's Add-On site and there are about 5 add-ons with that name. For the one you recommend can you give us it's full name and who it's by?

Ahh I see that.  Video DownloadHelper by mig  It has 3 balls a Blue Yellow and Red one.

@Xerxes0002 - Thanks! Hopefully it will help with some of those tutorial YouTube videos posted by others. Kind of hard to see what their doing and even worste / more grainy image when enlarged.

It does, I use it all over to grab the tutorials for local storage.  Of course it can only grab to the largest size posted, but I just tagem and let em download in the background.

@Xerxes0002 - I finally got around to try "Video DownloadHelper". After upgrading to Firefox 4 (which is brilliant) I couldn't use my regular add-on "Download Flash and Video" anymore.

Anyhoot "Video DownloadHelper" didn't quite work with some of the non YouTube videos, such as the embedded flash type.

Then I tried a few other add-ons that were compatible with Firefox 4 and finally settled with "FlashGot". It doesn't convert videos but that's ok anyway because I use Online-Convert.com.

BTW did I mention Firefox 4 is awesome. Feels a lot more slick and quicker than previous version. Also love the Menu Bar replaced by a drop down list. Gives me more web page viewing space. But I had to manually turn on the Add-on Bar again so I could see my "FoxClocks"; another nice Firefox add-on so I can catch those Renderosity fast sales before times runs out on the other side of the World. LOL.

FYI, RealPlayer already has a browser plugin that will download from YouTube and convert to AVI and it too is free. I know it works in both IE and FireFox. I haven't checked Opera, Safari or Chrome yet.