What are some alternatives?
When comparing Async and Slack, you can also consider the following products
FireRTC - FireRTC is the easiest way to call from your computer for free
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Unfuddle - Unfuddle is a secure, hosted project management solution for software development teams.
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
BobRTC - BobRTC is a VOIP platform dedicated to thwarting telephone fraud, illegal robocallers and scams.
Bitrix24 - Bitrix24 is a free (for small businesses) social enterprise platform. It is a united work space which handles the many aspects of daily operations and tasks. Create your own social intranet in minutes!