OK, changes in dpkg-dev 1.14.7 have forced my hand a little and dpkg-cross 2.0.0 has now been uploaded to Debian unstable (not experimental).
apt-cross 0.2.9 has been uploaded to Emdebian unstable - dependent on
dpkg-cross >= 1.99
apt-cross 0.3.0 has been uploaded to Debian unstable but will spend some time in the NEW queue (hence the 0.2.9 upload to Emdebian). apt-cross 0.3.0 is functionally identical to 0.2.9
emdebian-tools 0.3.9 has been uploaded to Emdebian unstable - dependent on apt-cross >= 0.2.9 and dpkg-cross >= 1.99
All three comprise extensive rewrites. apt-cross, in particular, is barely recognisable. dpkg-cross is a shadow of the former package and v2.0.0 signals the beginning of the long goodbye to both packages. dpkg developers expect to be able to merge all dpkg-cross functionality into dpkg before Lenny. Once that is done, it should be trivial to merge apt-cross behaviour into apt.
Only the new libcache-apt-perl package (containing the modified NorthernCross code from virtuoso) will persist. Once this whole transition is over, I'll upload Cache::Apt::* to CPAN so that it can become its own source package in Debian once apt-cross is removed.

IMPORTANT

dpkg cross-building support is HIGHLY EXPERIMENTAL!

Significant changes are still pending, including remapping the build paths during the
dpkg-buildpackage build and utilising the updated dpkg-shlibdeps code which is a decade ahead of what we had in dpkg-cross 1.39.

1. dpkg 1.14.7 included dpkg-buildpackage as a perl script instead of shell which breaks dpkg-cross <= 1.39 but the new code to support dpkg-cross >= 1.99 is not implemented yet.


2. The breakage that Zumbi experienced when using the dpkg version from
   experimental will now occur in unstable.
   http://lists.debian.org/debian-embedded/2007/09/msg00067.html. Note that this breakage would be severity "critical" if filed as a bug because it prevents not only cross-builds but normal Debian builds.


3. dpkg-cross 2.0.0 fixes this issue. Hence the urgency in uploading dpkg-cross 2.0.0


4. dpkg-cross 2.0.0 removes the old diversions of dpkg-buildpackage and dpkg-shlibdeps.


5. dpkg is set to support the removal of the dpkg-cross diversions and code to support this is coming this weekend. This means that there will be a GAP where cross-built packages will fail to find the correct shared libraries. HOWEVER, installing dpkg-cross 2.0.0 restores the ability to build normal Debian packages whilst keeping dpkg-cross installed. This is a far more important gain than a temporary problem in packages that hardly anyone is using yet (our Emdebian crossbuilt packages).

When dpkg-dev 1.14.8 becomes available, apt-cross, dpkg-cross and emdebian-tools will be updated to depend on this version.

Everyone: please note - cross-building support in Debian will be "fragile" for the next week or so. The rewritten packages are being uploaded against experimental dpkg support I expect bugs.

The benefits of these changes are:

1. The removal of diversions that are a decade out of date.


2. The implementation of virtuoso's NorthernCross code that transforms apt-cross and fixes lots of awkward bugs.


3. The incorporation of cross-building support in the heart of dpkg.


4. The beginning of the long goodbye to dpkg-cross and apt-cross.

RESULTS

With the new packages installed, some packages will produce:

 emdebuild: ERROR /usr/bin/ contains files for the wrong architecture!

i.e. the build appears to succeed but until dpkg-dev 1.14.8 includes support for looking for the correct libraries in /usr/$arch/lib instead of /usr/lib, we get unusable packages. This at least means that packages can be test built and the patches updated.