adx is a minimalistic but massively Web-enabled address book that runs completely in your Web browser. It's OS-independent and supports comprehensive details for each contact entry, including user identifiers and profiles for Skype, Twitter, Flickr, Delicious, Facebook, LinkedIn, studiVZ, instant messengers, etc. It supports the hCard and XFN microformats.
OpenInviter is a script to import contacts (address book data) from email providers like Yandex, Lycos, Rambler.ru, Live / Hotmail, OperaMail, GMX.net, Mail.ru, Mail.com, GMail, Yahoo!, Rediff, AOL, and KataMail. It can import from content management systems like SimpleMachines Forum (SMF), Drupal, Social Engine, Wordpress, PunBB, Joomla, JamRoom, and PhpBB. It also imports from social portals like Twitter, Facebook, Hi5, Friendster, Orkut, Myspace, and LinkedIn. It offers basic "tell a friend" features.
j-XChange is a pure Java implementation of the entire Collaboration Data Objects (CDO 1.21) library for accessing Microsoft Exchange Server in a platform independent manner. This library will allow interoperability with MS Exchange from all non-Windows platforms that support Java. This library is powered by j-Interop.
AtMail is a webmail client. The project aims to provide an elegant client for existing IMAP mailservers, with less bloat and a focus on an intuitive, simple user interface. Features include complete Webmail functionality, address-book support, video mail, an AJAX interface, drag'n'drop, and more.