On December 14, 2010, the Windows Live team has introduced a new subdomain of Live.com, featuring plug-ins for Windows Live Essentials. For example, you can find extensions for Windows Live Writer or Photo Gallery. These additional programs add new features to the applications. The name of the new site is plugins.live.com.
The process of adding your plugins to the directory has changed somewhat apparently, according to the Developer Information page. Instead of having to host the plugin files themselves, developers now have the choice of emailing the .msi files to Windows Live, who will then host and promote the plugins (or developers can choose to continue to self-host on SkyDrive and just send a link. The developer page has more information on the particulars of how to get your plugins listed.