FreeTDS (free implementation of the Tabular Data Stream protocol)

FreeTDS is a free implementation of Sybase's db-lib, ct-lib, and
ODBC libraries.  FreeTDS builds and runs on every flavor of unix-like
systems we've heard of, as well as Win32 (with or without Cygwin), VMS,
and Mac OS X. Failure to build on your system is probably considered
a bug. It has C language bindings, and works also with Perl and PHP,
among others.
