SIPphone supports open standards aggressively. They sell PSTN calling by the minute, claiming that most flat rate plans are a poor deal for the consumer. SIPPhone has even sued competitors that sell locked ATA devices without proper disclosure to the consumer.

via SIPphone –

SIPPhone offers three free softphones ( GizmoProject, X-Lite, and PhoneGaim ), and has a free-calling program All Calls Free under which registered users can call the landline and mobile phones of other Gizmo customers for free.