On the heels of my tests of T-Mobile's HotSpot@Home converged cell/Wi-Fi calling service, I put together a chart of the offerings: I've created a chart you can download as a PDF or view as HTML that compares the major combinations of service offerings for VoIP, Internet telephony, and their Wi-Fi components. For instance, Vonage and Speakeasy's Home VoIP service are both wireline voice plans that rely on an existing home broadband network. They're fairly close in intent to pure-play voice as a landline replacement.
In contrast, Skype's partners offer Wi-Fi phones but with the exception of Belkin's--treated separately--Skype phones are meant for unprotected, purposely open, or WEP/WPA/WPA2 secured networks. Few hotspots need apply. Belkin's Skype phone, with firmware I received and installed today, can use Boingo's $8 per month mobile service to access over 8,000 hotspots in the US and over 35,000 worldwide. (See article from earlier today.)
I'd welcome any comments on the chart. It's tricky to present online, as most tabular data is, which is why I've relied on PDF.