The following two sites appear to be SIP service
providers:
www.freeworlddialup.com/
Free World Dialup is Jeff Pulver's free service and definitely alive and
kicking...
I don't know them well enough to know.
Freeworlddialup provides a simple tool to evaluate
your
internet connection before trying their service.
The tool consistently claims that my port 5060 is blocked,
even though I am directly connected to my cable modem
and have all firewalls turned off. It seems like this
false result could be caused by an attempt establish
a 5060 connection to a non-existant voip server,
again supporting my theory that their server has been
shut down. Does this theory make sense?
As they are alive: No.
Also, both providers say that they work with
Windows Messenger 4.6 and 4.7 but not with 5.1.
Did Microsoft commit some crime in version 5.1
to make it incompatible
with third party SIP service providers?
I wouldn't say incompatible, they don't just allow third party SIP provider
accounts as they did in <5.0. I'm not sure what kind of crime you believe
may be commited, it's probably the well-known "it makes strategic business
sense"-crime.
g-)