The Alien package converter:

  Alien is a program that converts between redhat rpm, debian dpkg, stampede
  slp and slackware tgz file formats. If you want to use a package from
  another linux distribution than the one you have installed on your system,
  you can use alien to convert it to your preferred package format and
  install it.

Warning, alien can be dangerous:

  Despite the high version number, alien is still (and will probably always
  be) rather experimental software. It's been under development for many
  years now, but there are still many bugs and limitations.

  Alien should not be used to replace important system packages, like
  sysvinit, libc, or other things that are essential for the functioning of
  your system. Many of these packages are set up differently by the
  different distributions, and packages from the different distributions
  cannot be used interchangeably. In general, if you can't remove a
  package without breaking your system, don't try to replace it with an
  alien version.

Getting alien:

  The newest versions of alien are available at the alien home page; drop by
  http://kitenet.net/programs/alien/

  On metalab and its mirrors, alien is located in the
  pub/Linux/utils/scripts/ directory.

  You can also get rpm or deb packages of alien: 
  deb: ftp://ftp.debian.org/debian/unstable/binary-all/admin/alien_*.deb
  rpm: ftp://ftp.redhat.com/pub/contrib/noarch/alien-*.rpm

Other things you'll need:

  To use alien, you will need several other programs. Alien is a perl
  program, and requires perl version 5.004 or greater. If you use slackware,
  make sure you get perl 5.004, the perl 5.003 in slackware does not work
  with alien!

  To convert packages to or from rpms, you need the Red Hat Package Manager;
  get it from Red Hat's ftp site.

  If you want to convert packages into debian packages, you will need the
  dpkg, dpkg-dev, and debhelper packages, which are available on the Debian
  ftp site.

  To convert to/from stampede packages, you will need bzip2, get it from
	http://sourceware.cygnus.com/bzip2/index.html

  Attention, Slackware, Red Hat, and Stampede users: Bruce S. Babcock
  <babcock@math.psu.edu> has put together an "alien-extra"
  package of all the extra files you need to use alien on
  a Red Hat or Slackware system. (Debian systems automatically have the
  required files.)
  The Slackware version is at 
  	ftp://ykbsb2.yk.psu.edu/pub/alien/alien-extra.tgz
  The RedHat version is at
  	ftp://ykbsb2.yk.psu.edu/pub/alien/alien-extra.rpm
  The Stampede version is at
  	ftp://ykbsb2.yk.psu.edu/pub/alien/alien-extra.slp

Programs that use alien:

  I know of one program that acts as a frontend to alien - kpackviewer is a
  package viewer that can convert between package formats by using alien. Its
  homepage is at http://www.momentus.com.br/users/hook/kpackviewer.html

Please report any bugs in alien to the author: 

  Joey Hess <joey@kitenet.net>