There are lots of applications that were CASified thanks to phpCAS. Feel free to add yours!

pNews is an NNTP reader written in PHP. It is CAS-compliant since v2.3.0 thanks to phpCAS (CAS-ified by Pascal Aubry, integrated by Shen Cheng-Da).

Horde IMP, the famous PHP webmail was CAS-ified by Julien Marchal. A paper presented at EUNIS2004 describes how it works with a Cyrus IMAP server, see also another paper in French. A CAS-compliant version of Horde IMP can be downloaded from the download area of the ESUP-Portail project.
A more generic implementation based on UW-IMAP and imapproxy can be found at the Horde Wiki :: CASAuthHowTo.

Tikiwiki, a PHP CMS, was CAS-ified by Terence Chiu using phpCAS 0.4.8.

Mantis, a Bug Tracking System, was CASified by Robert Legros. For more information, please refer to http://bugs.mantisbt.org/bug_view_advanced_page.php?bug_id=0004234.

SPIP, a multilingual Content Management System (CMS), was CASified by Fabrice Jammes. The plugin of SPIP can be download on the ESUP portal. More detail on the installation can be found at http://casldapauthspip.univ-paris1.fr/