Zoiper - Cross-platform VoIP softphone dialer for SIP and IAX systems
EZ Texting - EZ Texting provides SMS marketing solutions to businesses of all sizes.
MicroSIP - MicroSIP is a free portable SIP softphone for Windows based on PJSIP stack.
Textmagic - The all-in-one solution for all your business texting needs - marketing campaigns, two-way SMS chats, reminders, notifications, and internal staff communication.
Linphone - Linphone is an internet phone or Voice Over IP phone (VoIP).
SimpleTexting - SimpleTexting offers SMS and text marketing services for companies of all sizes.