This is an old revision of the document!
https://wiki.sangoma.com/display/CONNECT/Introducing+Sangoma+Connect
https://meet.sangoma.com/
https://www.counterpath.com/product-comparison/
https://www.sessiontalk.co.uk
The free version works well.
Additional paid business features:
http://www.grandstream.com/products/ip-voice-telephony/softphone-app/product/grandstream-wave
https://www.zoiper.com/