There's a lot of buzz in the US at the moment about GrandCentral, which is part Web 2.0 service, part telco. You can sign up for one unified telephone number, which allows some interesting features, such as: call forking (so that all your phones can ring when someone calls your one number; voicemail customized to the caller; color ringback tones, all managed through a common web interface. It's an interesting showcase of what can be done where traditional telephony bumps into the web. Some of this could be achieved through traditional SS7 signalling, and some of it is probably in the SIP/VoIP domain. Good luck to them, but I shall have to wait to experience it, as it only works in the USA and Canada today.