PSGw

RSdevs has created a gateway (PSGw) to let Skype communicate over SIP or H323 to communicate with other systems like an Asterisk PBX. In other words; An unified interface to several VoIP networks (SIP/H.323/Skype) in a single application.

Here's how it works:

1. User makes a SIP URI call (using SIP phone or softphone) to a domain where the PSGW software is located. For this example, suppose I have it running on my domain: tmcnet.com. Thus, you can simply SIP dial <username>@tmcnet.com
2. The call is routed to the tmcnet.com firewall or SIP proxy with port 5060 mapped to a PC running Skype and the PSGW software.
3. The PSGW takes the SIP call, strips off “<username>” from <username>@tmcnet.com and then initiates a Skype call to Skype user “<username>”. (Thus, you simple need to pre-pend the Skype username you wish to call to the domain.)
4. The PSGW then “bridges” the audio from the Skype leg of the call with the SIP leg of the call.

That's it! You've just made a SIP-to-Skype call. Skype's Great Wall of VoIP has just been breached! Granted, it is a bit of a "kludge" requiring a host PC running Skype & PSGW, but cool stuff nevertheless, eh?

(source)