Yeallink has built this small ATA adaptator , distributed in france with the Wengo SIP service , and with a lot of providers arguing it works with skype.....

This USB box acts as a USB sound card and thus is recognized on Linux BUT a command has to be sent to the box via USB so it can be used as a sound card. Then you can find information about how to drive this box for your application on the linux API project page

NEW : an official GPL'ed project is born to fully support those USB-Box ( rapidbox , skypebox , callmebox)

Savannah usbb2k page

This is based on libUSB and so will work on Windows, MacOSX and Linux and even GFreeBSD I guess

Seems to work for all yealink product Usb-p1k, b1k etc...

For the moment ( may 2005) it works on linux and all functions are supported , binary realease will come Soon , First int駲ation will be for linphone , KIAX and gnomemeeting , No skype client planned .....

Software for windows can be found on the providers pages

The USB-P1K works really fine with Counterpath X-Lite and X-TenMate (http://www.yealink.com/en/otherdown.asp)
the most stable version is X-Lite build 1103 and XtenMate version 1.0.0.15 since the new versions of both
have some problems