Telstra Clear looks very interesting from afar.
It's a hosted VoIP service designed for the five or more type offices. What I find interesting though is it is woven over the fabric of the telco network in New Zealand.
This means integration from the core to the edge, and a single source provider. It's what I think Verizon is hoping to do with FIOS, and what AT&T will never achieve with U-Verse, which is looking like ISDN all over again for the giant telco here in the USA.
The official web site is here for Telstra Clear.