Debian Packages
HylaFAX for Debian has been split in two packages: hylafax-server and hylafax-client.
Here you may find the packages for the stable version and for the testing version of Debian. Follow the binary package names in either page.
You may even try the unstable packages, but please note that this will not be the latest CVS snapshot: all Debian versions are derived from HylaFAX official releases.
The list of open bug reports is always available here.
Since HylaFAX is included in the Debian archive, if you want to install it, just issue, as root, this command:
apt-get install hylafax-server hylafax-client
The last version uploaded in Debian is 4.4.4. It is included in Debian 5.0 "lenny". This version is also available for the previous Debian release (4.0 / "etch") as backported packages, see backports.org for further details.
Apt repository
Aidan Van Dyk (aidan@ifax.com) keeps an up to date apt repository containing the most recent versions of HylaFAX for debian and derivatives. To use it, add the following lines to your apt.sources:
deb http://code.highrise.ca/apt/ <Distro_Name> <HylaFAX_branch>
See http://code.highrise.ca/apt/ for more details.