Here is a patch for adding pkg-config support to libmad.
It would make life a bit easier for distro maintainers if this was applied.
In case you didn't know, pkg-config is a tool for providing LDFLAGS and
CFLAGS for packages using shared libraries. It's on freedesktop.org.
Debian has already been distributing the pkg-config file mad.pc with
libmad for some time, and people developing on debian (notably xmms2 
developers) have started relying on this support being present, causing
some confusion for people installing from source and on some BSDs which
do not provide mad.pc (google: pkgconfig libmad).

EMH

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diff -Naur libmad-0.15.1b.old/configure.ac libmad-0.15.1b/configure.ac
--- libmad-0.15.1b.old/configure.ac	2004-01-23 10:41:32.000000000 +0100
+++ libmad-0.15.1b/configure.ac	2004-08-07 02:25:24.633462168 +0200
@@ -429,5 +429,5 @@
 dnl AC_SUBST(LTLIBOBJS)
 
 AC_CONFIG_FILES([Makefile msvc++/Makefile  \
-	libmad.list])
+	libmad.list mad.pc])
 AC_OUTPUT
diff -Naur libmad-0.15.1b.old/mad.pc.in libmad-0.15.1b/mad.pc.in
--- libmad-0.15.1b.old/mad.pc.in	1970-01-01 01:00:00.000000000 +0100
+++ libmad-0.15.1b/mad.pc.in	2004-08-07 02:04:59.617692872 +0200
@@ -0,0 +1,14 @@
+# libmad pkg-config source file
+
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: mad
+Description: MPEG Audio Decoder
+Version: @VERSION@
+Requires:
+Conflicts:
+Libs: -L${libdir} -lmad -lm
+Cflags: -I${includedir}
diff -Naur libmad-0.15.1b.old/Makefile.am libmad-0.15.1b/Makefile.am
--- libmad-0.15.1b.old/Makefile.am	2004-02-17 03:02:03.000000000 +0100
+++ libmad-0.15.1b/Makefile.am	2004-08-07 02:03:19.859858368 +0200
@@ -24,6 +24,9 @@
 SUBDIRS =		
 DIST_SUBDIRS =		msvc++
 
+pkgconfigdir =		$(libdir)/pkgconfig
+pkgconfig_DATA =	mad.pc
+
 lib_LTLIBRARIES =	libmad.la
 include_HEADERS =	mad.h
 
@@ -34,7 +37,8 @@
 minimad_LDADD =		libmad.la
 
 EXTRA_DIST =		mad.h.sed  \
-			CHANGES COPYRIGHT CREDITS README TODO VERSION
+			CHANGES COPYRIGHT CREDITS README TODO VERSION \
+			mad.pc.in
 
 exported_headers =	version.h fixed.h bit.h timer.h stream.h frame.h  \
 			synth.h decoder.h