BioCluster is a peer-to-peer clustering platform for Asterisk, the open source PBX, which allows Asterisk to be used as a full carrier-grade telephony solution. It is meant to be installed on several machines together with Asterisk, turning them into a VoIP cluster. While the BioCluster peer-to-peer protocol was initially designed to cater to Asterisk-based clustering solutions, the BioCluster framework is capable of being extended to support various forms of normally unclustered devices or software packages.
Bluel VMail is a semi-complete voicemail system that supports automated attendant, call transfer, e-mail delivery of voicemail messages, etc. It was designed to work with the Diamond SupraExpress ISA modem and Panasonic KX-T61610 hybrid phone switch (cheap!), but is probably portable to similar configurations.
BtFree is a library for creating client-server applications that communicate over a Bluetooth connection. You can use it in your MIDP application or in a Java application that uses an implementation of JSR82. It allows you to create applications with client-server interaction easily, avoiding the need to know JSR82 and the problems related.
CT Server is a Perl module that interfaces with Voicetronix computer telephony cards, giving developers a method of creating quick and creative computer telephony applications. A complete PBX is included as an example, which includes a Web interface for configuring and monitoring the PBX.