Slack's two million users don't just use Slack--they live in it. The average user is connected, on one device or another, for 10 hours a day, way too much time to spend messaging one's co-workers, however enjoyable Slack may make that. In fact, only about two hours and 15 minutes per day is active Slacking.

Fortunately, a growing flotilla of integrations and native applications makes it possible to make the most of those other seven-plus hours to get stuff done within Slack's environment. To make it even easier, the startup (Inc.'s Company of the Year for 2015) has created an $80 million fund to invest in early-stage startups developing apps for its ecosystem. A bevy of venture capital firms, including Slack investors Accel, Andreessen Horowitz, and Social + Capital, joined Slack in stumping up money for the fund. 

"There's a whole new class of developers out there that are building applications, and they're building them on Slack first," says April Underwood, Slack's head of platform. "My hunch is there are hundreds if not thousands of small teams out there thinking about how to solve problems at work. I've personally met with dozens."

Many of these startups are finding ways to take tedious or time-consuming workplace tasks and make them easier with a conversational user interface in the form of a chatbot. Underwood cited Birdly, a virtual assistant that lets you file your expenses through a dialogue with a bot named Bill. She also name-checked Growbot, a feedback tool that monitors team conversations and keeps track of "wins." 

As Slack grows as an ecosystem, third-party integrations are becoming a bigger and bigger part of its draw. The company says users have installed 4,000 different integrations some 2.2 million times. To make it easier to find the right one, Slack is also launching an "App Directory." It's not an app store per se, says Underwood, because Slack won't be taking a cut of any sales. At least not right away; Underwood makes it sound like that's something that could happen down the road. The App Directory will feature 150 integrations at launch. 

For now, Slack's revenue is already growing plenty fast on sales of its premium service tiers. When I finished reporting my Company of the Year story in October, Slack's 480,000 paid seats gave it an annual recurring revenue of $45 million. Just since then, paid seats are up to 570,000 and ARR has grown to $50 million.