Votum for Slack - Crowdsourced lists with upvotes, inside Slack
Lurchr - Saves all your Slack links, so you can focus on work
Must-Read for Slack - Build controllable must-read lists for your team in Slack.
Slack News Feed - Get the top posts from every Slack chat you're in.
Corpus - Curate, take notes and share your reading list
Tettra - Tettra is a company wiki that helps teams manage and share organizational knowledge.