Zulip is the only modern team chat app that is designed for both live and asynchronous conversations. Zulip topics create a separate space for each discussion, so different conversations will never get in each other's way.
Trillian is an instant messaging app that works on phones, tablets, and desktops while keeping your chats neatly synchronized between all of them! We think conversation should be easily shared between all of your devices, not trapped as text messages on your phone.
Google Voice gives you one number for all your phones, voicemail organized in an email format, free US long distance calls, low rates on international calls, and many free calling features, including transcripts, call blocking, call screening, conference calling, SMS, and more.
Google Voice vs Line2 opinions
Free and does many of the same things
MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack. It allowing to do high quality VoIP calls (P2P or on regular telephones) via open SIP protocol. From cloud of SIP providers you can choose best for you, register account and use it with MicroSIP. You'.
Messenger for Desktop is a wrapper for the official client messenger.com. Therefore it works like a regular browser which can only navigate to the messenger.com web app. MFD doesn't touch your messages, account or personal data. All that is handled securely by Facebook.
Be careful during the installation: https://alternativeto.net/discussions/applications/11718/be-careful-in-the-installation/
Messenger Kids is a free video calling and messaging app designed for kids to connect with close friends and family from their tablet or smartphone. Kids can only connect with parent-approved contacts, which creates a more controlled environment.
Phoner provides business owner, sales people, lawyers, doctors, police officers and others with a second phone number to protect their identity and also gives the convenience of multiple phone numbers on one device.
Access phone numbers from any device with internet: supports voice, SMS, MMS (pictures and group texting). Entirely open source stack and works over open protocols (XMPP).