There are 2 repositories under sitecore-extensions topic.
Sitecore Install Extensions
A google Chrome extension that brings a set of handy tools for Sitecore's authors.
A library of core helpers, extensions, constants, enums and other useful things for Sitecore CMS projects.
Css Picker field for Sitecore CMS
CopyPageToVersions is an extension for the Content Editor and the Experience Editor. It provides a dialog for content editors, where a page in a specific version can be copied to a selectable list of language versions.
Storage data to the local file system when Sitecore first launch.
Pre-release feed for Sitecore Extensions browser extension for Sitecore CMS
the inverse of Sitecore.Ship: allows you to grab a serialized version of an item from a remote server
Autocomplete Single-line Text Field for Sitecore CMS