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.
mptc is a Perl script to help you work out whether you're on the cheapest mobile phone network/tariff for your phoning habits. You feed it an itemised phone bill and tariff pricing information, and it will tell you how much that bill would have cost on different tariffs. So far it only supports UK network pricing systems, but could easily be extended and applied in other countries.
Thunderbolt is a middleware infrastructure suite that includes connectors, Java development libraries, a business process design GUI, and a system monitor GUI. It is appropriate for both telco and financial services. It provides the basis for a simple, efficient integration infrastructure which can be easily extended. While maintaining a SOA in mind, it can easily orchestrate Web services and legacy systems. It's also useful for developing proof of concept projects requiring processing in real time, batch, or both.
The REMWAVE Carrier Core platform is a stable platform to set up a voice over IP carrier (ITSP). It contains a complete billing, rating, and routing engine and is used by some of the largest ITSPs. The Carrier Core is free for deployment and contains a billing engine (based on Oracle express 10g edition, though larger editions are available), a SIP proxy and registrar, a customer care system, and templates to set up a customer self service portal.
The 3Gdb Home Subscriber Server implements the HSS network element within an IP multimedia subsystem (IMS) core network (CN). An IMS CN is a collection of SIP proxies, registrars, and servers used for the provision of services in a 3GPP all-IP mobile network. The HSS provides a centralized data base for subscriber records and generates authentication vectors.