Using Streams as a personal workspace
Streams are great for team communication, but you can also dedicate a stream as a personal workspace. Just create a stream for yourself only and label it however you want.
Think of it kind of how you'd think of Slacking yourself a reminder or typing up a message to Slackbot. Leave notes, brainstorm ideas, copy and paste a link to a NYT article to read on your commute later, or drop in a file.