SIP can be downloaded from thekompany. At the same site you also find latest news and a lot more of information. There is also a mailing list and archive.
SIP (as in the original package) runs on Linux (or other unix systems). Bindings (incl. the required SIPLIB) also run on Windows.
It turned out that porting SIP itself wasn't too difficult, I've set up a Visual C++ projects for both. I hope this matures enough to finally find its way into the SIP distribution. Mail me if you want it earlier.
See the INSTALL file for the generic UNIX build and installation instructions.
See the INSTALL.win32 file for the generic Windows build and installation instructions.
In order to compile and install SIP on your system, type the following in the base directory of the SIP distribution:
% ./configure % make % make install