OpenPhone - Simplest way to own a business phone number
Grasshopper - Grasshopper enables entrepreneurs to build a virtual office that connects callers to employees, wherever they are.
Burner - Disposable phone numbers -- now with MMS photo support
Vumber - Toll Free or Local Numbers for Your Business
TextNow - TextNow is a mobile virtual network operator (MVNO) that provides a free phone service to users by using other cellular networks coverage.
Dialpad - Switch is a cloud-based phone system built for Google Apps users.