The Autoconf Macro Archive aims to provide a collection of reusable
Autoconf macros as free software. The archive currently features more
than 300 macros which perform portability tests ranging from compiler
support for weird language extensions to automatic generation of
sophisticated Automake rules.  However, all these macros have been
contributed by friendly supporters of the cause from all over the
Internet; the archive really just collects and distributes them.

WWW: http://autoconf-archive.cryp.to/