These are the packages needed on Debian 4.0 (Etch) for XEN:

python-twisted, binutils, zlib1g-dev, python-dev, transfig, bzip2,
libcurl3-dev, libncurses5-dev, x-dev, build-essential, gettext,
libsdl1.2-dev, libvncserver-dev, libxml2-dev, libjpeg62-dev, tetex-extra,
gs-common, udev, graphviz, bin86, bcc

hg clone http://xenbits.xensource.com/staging/xen-3.0.5-testing.hg
hg clone http://xenbits.xensource.com/staging/xen-3.1-testing.hg
hg clone http://xenbits.xensource.com/staging/xen-unstable.hg
hg clone http://xenbits.xensource.com/xen-3.0.4-2-testing.hg
hg clone http://xenbits.xensource.com/xen-3.0.4-testing.hg