FriendFeed

Universal Inbox/Universal Outbox

FriendFeed was a real-time feed aggregator that consolidated updates from social media and social networking websites, social bookmarking websites, blogs and microblogging updates, as well as any type of RSS/Atom feed. It was created by Bret Taylor, Jim Norris, Paul Buchheit and Sanjeev Singh. https://en.wikipedia.org/wiki/FriendFeed

Here's a nice screenshot of someone's home-page showing updates from multiple users.

https://www.askdavetaylor.com/how_to_add_google_reader_shared_items_to_friendfeed_account/