Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
TextNow - TextNow is a mobile virtual network operator (MVNO) that provides a free phone service to users by using other cellular networks coverage.
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Google Voice - Google Voice gives you one number for all your phones, voicemail organized in an email format, free...
Facebook Messenger - Facebook Messenger is a faster way to message.
Burner - Disposable phone numbers -- now with MMS photo support