Here are some hand picked Known plugins that you may find useful. You can find more on my Github profile.
Flickr Importer: This is a console plugin that allows you to import an export from your Flickr profile into Known.
Video Transcoder: Transcode uploaded videos into something web friendly (useful when combined with the Flickr Import above).
Lightbox: Display photos nicely in a Lightbox popup.
Akismet Spam Filter: Basic anti-spam filter for comments on your Known site.
Bitly Link Shortener: Automatically shorten your shared links.
Two Factor Authentication: Adds 2FA support to your Known site, supports the Google Authenticator.
If you’ve found any of these useful, then please consider contributing to the Known project, so that I can keep doing this!