tkbiff allows arbitrary commands to be executed upon mail reception. If you like programs such as xbiff and xbiff++ but wish they were more flexible, then you'll like tkbiff. Unlike other biffs, tkbiff is fully customizable. tkbiff also doesn't waste your valuable screen space with icons; instead, it shows you the mail itself. It supports UNIX, Mac, and Windows, IMAP, POP, and UNIX-style mail files, and SSL and APOP.
R-AddressBook is a Java address book which stores its data in XML format. It can be run on virtually any computer (including PDAs) and offers local and global address information storage, WebServices based synchronization, off- and on-line operation, no restriction on the type or number of fields for each entry, and automatic address updates.