mod_psldap is an Apache module that performs authentication and authorization against an LDAP server with LDAP based session management. It also provides Web 2.0 based capabilities to add, edit, move, and create new records in the LDAP store, leveraging XSL stylesheets to offload heavy processing to the clients and reduce bandwidth consumption by up to 95% or more.
XFMail is an X11 application for receiving electronic mail. It implements most of its email functionality internally so that it does not depend on a lot of extra packages. It supports POP3, MBOX, IMAP4, sendmail, and SMTP. It has built-in support for interfacing with PGP, GPG, ispell/aspell, faces, LDAP, and esound. It runs on most Unix variants.
Libvc is a vCard library which was written using 'flex' and 'bison'. It handles scanning a vCard file, parsing the vCard file into a data storage structure, manipulating the data storage structure, and writing the structure back to a file. It was originally written for 'rolo', but has been split off for general use.
Otak provides a visual interface to command line programs that don't have one, that allows users to select arguments from a menu. For example, it can be used as an address book program with Mutt (the default), or as a phone book with SMS sending software, or even as a list of hosts for SSH or FTP.