The more, the merrier... ;-)
might as well take a gander at leaner (1Mb) http://www.ravib.com/youtubepal/
(requires .NET Framework 3.5 SP1)

Since we're debating preferences here, let me point out 3D Youtube Downloader (http://www.portablefreeware.com/?id=2634) as another excellent alternative...

This one is better, IMHO. It will download and convert to different formats including MP3. http://www.youtube-d.com/download.html

AFAIK, it uses ffmpeg as the download engine (as do most YouTube downloaders) - and I daresay a large part of that size is due to having simply to include the various ffmpeg files.

I do have browser addons for this, but those tend to break with every dreaded youtube redesign, so an app like this can be useful. I just don't get the enormous (11MB packed/27MB unpacked(!)) size of this. It's supposed to just downloads video's. Why does it need to be this huge?

I like to use this online application, http://www.downloadvube.com/
It seems to support conversion but I haven't used it yet. Anyway, I'd like to try when I need to convert, and I would like to share if it is easy to use.

They FINALLY updated the embedded FFmpeg:

from Fabrice Bellard build
FFmpeg version SVN-r16573 built on Jan 13 2009 02:57:09 with gcc: 4.2.4

to Zeranoe build
FFmpeg version N-57235-g0bf8580 built on Oct 17 2013 18:02:03 with gcc 4.8.1

Note: the FFmpeg Zeranoe build (static 32-bit) used/embedded can be found at:
http://ffmpeg.zeranoe.com/builds/win32/static/
using either the GIT version # or 'built' date

Try TubeMate (for Android).
http://tubemate.net/

DaniPorat: there isn't really a good mobile download program yet since Google owns the mobile market and they've blocked YouTube downloaders from their app market. Apple may or may not have done similarly. Upcoming VLC or Songbird software updates may have workable system that may involve syncing with Mac/PC.

Tried it out, does seem to work pretty well, but no mobile app (which is kind of what I was looking for since I usually use the torch browser for downloads to PC, but haven't found a good way to download to mobile).

@shodan816

Both Free YouTube Video Download and Free YouTube Downloader Converter are nagware.

This one is far better. It will also convert to mp3 format.
http://www.hide-windows.com/free_youtube_downloader/youtube_converter.htm

@ Ruby: O.K., thanks ;)

@Checker
This dev stays on top of YouTube changes and tweaks his code accordingly.
E.G. I just tried to download http://www.youtube.com/watch?v=fm-xw6Lap_4 Petrucci's new title cut from their new album using 2.9.8.4 (2012.07.26) and it failed however 2.9.8.9 (2013.08.09) succeeds.

What has been changed, except of the version number, from v2.9.8 - 2.9.8.1 ... 2.9.8.7 ?
Exact same size, exact same changelog.

Additional note: because YouTube no longer caches whole videos locally, I've found sometimes this is necessary on slow connections to be able to watch a video from beginning to end without several annoying pauses in the middle.

I use a userscript for this:
https://userscripts.org/scripts/show/25105

For Opera users, use the extension:
https://addons.opera.com/addons/extensions/details/download-youtube-videos-as-mp4/

Recent versions sometimes have difficulty with especially large (over 100 minute) files. When downloading FLV files, I've had to restart downloads a few times, even on a very fast and reliable network (MP4 settings seem to work better). Still my favorite downloader & use along with Pazera Audio Extractor to get/convert audio.

Finally tried it and I would consider it adware because that button in the upper left changes-donate,download multiple videos at the same time and a couple more-if you click the download multiple videos button it redirects to a page to purchase another product-I dont know.....plus my email was sluggish after using it,removed it and email is fine?

I see my question was answered-I emailed the
author 2days ago!

I have not used this yet but has anyone used it in the last 2 days as youtube changed the code they use and none of the firefox download extensions work anymore?

It appears V2.9.2 is back to 'Stealth' status as it is now/again using the included ini

I've updated the database to reflect

This is a great YouTube downloader, but I wish the author would have the app check in it's own folder for it's INI file first instead of automatically creating a folder under the User folder. Then it would be truly portable.

This program can download HD [720p] and Full HD [1080p] if available on the YouTube Video.

If you start with 1080p and it's not available, it asks if you would like to download the next available, e.g. 720p etc..

Conversions to AVI [Xvid] and MP4 are done using an embedded FFmpeg version SVN-r16573

It now saves its setting(s) to the included ini.

Unlike many similar tools, the developers are doing a great job keeping up with the program and changes in Youtube services. Great program.

Portable Opera + Good Youtube extension = ^_^

I'd rather use a browser's plugin / extension for this than rely on a program.

Thanks, i seached everywhere YouTube downloader HD 2.5 version Portable, and now finally i found this. :D

This app creates a copy of its ini file i the user's ApplicationData folder

Nice, but where is link to latest 1.8.1 portable version ???