Use this elgg plugin to display a login form on external sites, other directories or subdirectories, or even in local files.

Log In Required is a plugin that secures elgg by preventing non-members from accessing all but some pages open for public viewing.

wp-PluginInstaller is a plugin designed to allow plugin writers help their site visitors automatically install plugins in their WordPress installations without the need to download and upload the plugin zip file.

Tweet Import is a WordPress plugin that imports twitter posts from multiple twitter accounts, favorites, and lists to WordPress. It provides the option to import to different categories, supports several tagging and #hashtag related options.

A yiiFramework extension, takes a combination of Model attributes and verifies uniqueness of the combination in the database table. Plugin Links Extension Page at the yii Framework website