Parent page: Internet and Networking
These are a few options:
Ekiga (previously known as Gnomeeting)
Qutecom (previously known as Wengophone)
x-Lite (Non-free propriety)
They all seem to be in development, but the pace seems to be slow. SFLphone seems to be the only softphone that supports PulseAudio out of the box. SFLphone and Twinklephone are reported to work properly with SIP implementations using Asterisk, but other SIP phones should be compatible with that as well.
SFLphone is the most suitable softphone for companies, as it is the only softphone in the list to support attended transfer. It also supports a wide range of codecs, as well as conference calls.