I provide an unofficial Debian apt repository for HEP related packages which includes the CLHEP libraries and KtJet, users of testing,unstable or sarge on i386 can add the following lines to their /etc/apt/sources.list (replace testing with stable or unstable if you prefer to use those distributions):

deb http://www-pnp.physics.ox.ac.uk/~ferrando/debian/ testing hep
deb-src http://www-pnp.physics.ox.ac.uk/~ferrando/debian/ testing hep
deb http://lcg-heppkg.web.cern.ch/lcg-heppkg/debian sid hep
deb-src http://lcg-heppkg.web.cern.ch/lcg-heppkg/debian sid hep
                

also the original desy repository still exists as a mirror:

deb http://www-zeus.desy.de/~ferrando/debian/ testing hep
deb-src http://www-zeus.desy.de/~ferrando/debian/ testing hep

then packages can be installed, the usual debian way, with e.g.

apt-get update
apt-get install clhep2 clhep2-dev ktjet ktjet-dev

A debian package can be built on the machine with:

apt-get update
apt-get source -b clhep2

The presently available packages are listed here .
The presently available Source packages are listed here .

The following debian distributions have packages: sarge, etch, sid

CLHEP packages are distributed with the permission of the CLHEP authors - licensing issues for official debian distribution remain unresolved

Latest CLHEP versions available for i386: 2.0.4.0 (clhep2), 1.9.3.1 (clhep)
Latest KtJet version available for i386: 1.0.8

Kevin McCarty provided amd64 builds of the clhep packages, so I believe the sources line above should work for users of that architecture, the packages are listed here (testing/unstable).
Many thanks to Kevin for making these available and for his advice on improving the packages.

Frederic Lehobey and Carlo Segre built versions of clhep2 for the powerpc architecture, so the apt sources line should also work for that architecture. See the packages available here (testing/unstable). Thanks to Frederic and Carlo for providing their builds.
Carlo Segre provided builds for the mips and sparc architectures. Packages are available for sid (mips,sparc) and sarge (mips,sparc).

The root package currently provided is called root-cern and has cernlib enabled (dependencies are presently not handled correctly). There is no plan to provide paw , since it's already part of the Debian distribution. I will no longer update my root package because there are better ones available at http://mirror.phy.bnl.gov/debian-root/. ROOT is now in the official debian experimental distribution!(package is called root-system) - expect it in unstable/Sid soon.