GeoGebraTube: More than 12000 applets and counting
Applets in GeoGebraTube can be downloaded (including the GGB file), embedded in blogs or websites, or shared to colleagues and friends using social media sites.
Recently, the site has also allowed Google, Facebook, and Twitter login making it even more accessible to a lot of users. Of course, the old GeoGebra Forum login name and password can still be used.
Note: The image in this post is in my banner. This is probably a WordPress bug.