CLI alternatives for downloading from YouTube or other flash video streaming sites:
Package: get-flash-videos
Syntax:
get_flash_videos [OPTION]... URL...
with specified URL of the video.
get_flash_videos [OPTION]... SEARCH
where SEARCH is the video-name/string to search for in Google Videos.
Supported sites:
Supports many video sites including
- YouTube,
- eHow,
- Brightcove (used by many sites like Channel 4, Daily Telegraph ...),
- BBC (news, etc),
- Metacafe,
- aol,
- Google,
- fliqz,
- nicovideo,
- vimeo,
- Blip,
- Break,
- Collegehumor,
- Sevenload,
- Wat.tv
Package: youtube-dl
Syntax:
youtube-dl [options] url ...
Some of currently supported sites:
- CollegeHumor,
- Comedy Central,
- Dailymotion,
- Facebook,
- Metacafe,
- Photobucket,
- The Escapist,
- Vimeo,
- Yahoo!,
- YouTube,
- blip.tv,
- video.google.com,
- Soundcloud,
- InfoQ,
- Mixcloud,
- OpenClassRoom
Mozilla Firefox add-on:
Update: Merging my other answer for this post.
This one's been my favorite Firefox addon: Flash Video Downloader

Currently supported sites:
- YouTube,
- Google Video (video.google.com),
- DailyMotion (dailymotion.com),
- Metacafe (metacafe.com),
- Break.com (break.com),
- Blip.tv (blip.tv),
- MyVideo.de (myvideo.de) and others.
Also allows for flash games download from:
- gamespot.com,
- community.games.com,
- armorgames.com,
- net-games.biz,
- gamesvine.com,
- zoopgames.com,
- flashgames247.com and more.