Userscripts.org

Download Youtube Videos (HD 1080p & 720p/HQ MP4, Mp3, FLV, 3GP) Dailymotion (HQ MP4, FLV), Magavideo (HD/HQ FLV) Google (HQ MP4, FLV), Vimeo (HQ MP4) Break (HQ MP4, FLV), Veoh (HQ MP4, FLV), Metacafe, Spike, Myspace, Facebook, Current, Redtube and...

Adds FLV, MP4, 3GP, and 720p download links to YouTube.

Removes video advertisements

Enhances your pirating experience by adding torrent links to iMDB, Rotten Tomatoes (and MovieFone, soon).

Adds a button to download any tube on Youtube, Google! Video, Dailymotion, Veoh, Yahoo! Video and much more

Adds the national flag icons next to each username in the comment section of Youtube.

Adds &fmt=18 to the url for high quality but not if any &fmt=x already exist and adds &fmt=18 to all the links

Changes download button to FLV video file on Extreme Tube. Use with a download accelerator like free download manager means videos are downloaded in no time.

Removes main youtube ads, does not remove in-video ads.

Watch videos in high quality automatically. Now has a UserScript command to toggle a confirmation box. Made for people who don't login or save cookies. Uses JavaScript instead of &fmt=18; no reloading pages

Adds a button that redirects to KeepVid's YouTube download service for the video you are currently watching.

Completely removes the annoying gray playlist at the bottom of YouTube. (In opposition to just hiding it.)

Hides comments, preserves brain cells. Click headers to toggle.

Changes javascript links into direct links

Customize YouTube's Player Page

Adds a menu under YouTube video with available MP3 files found on ZippyShare and Hulkshare.

Stop Autoplaying Video On YouTube Profiles

Automatically "likes" videos from users you choose, or anybody.

Gets right of the footer, copyright, google ads, big frontpage ad, side announcement box, "may not be suitable for minors" warning, and other annoyances.

Automatically pauses the video when you switch to a different tab or window, and automatically plays when you come back to it

Strips YouTube's interface down to a bare nothing and optimizes load time.

Adds extended functionality to the youtube player such as player refreshing if video stops loading, user specified seek ahead, stop video loading, and more

Shows hidden thumbed-down comments that can't normally be seen

Several customizable options. Special support for Userscripts.org (new interface, fix for pre tags, and allows you to hide the install warning box and footer) Changes text fields, buttons, links, selects, and text areas.

Switches to YouTube's HQ version quickly (no reloading)

Hide the videos you've already seen

Uses the JW Player for youtube. Has options in the user script commands

Removes unnecessary parameters from links like feature=channel

Adds a "By Date" button next to the search button

Adds &fmt=18 to all YouTube links