What are some alternatives?
When comparing pop.in and Many to Slack, you can also consider the following products
Lipoker - The easiest way to play poker online with friends
Slack Archive - Public, searchable & browseable archive of Slack channels
EasyPoker - Host poker nights without chips or playing cards
Islands - Slack for College 🌴
Whale - Video Q&A with influencers and experts 🐳
Chalk - Chalk is a calculator that tries to do right what others do wrong.