OnSIP.com is a free setup we use. It's meant to be a way to test and
talk in g722 wideband (+ optional video) amongst regular participants
of the VUC.
Adding large numbers of users isn't practical because it requires me
to manually add them. There is no way people can add themselves,
unfortunately, because this is a business-oriented service.
http://ideasip.com is a great free service you can use if you want a
FWD replacement or a SIP to SIP server. Is Voxalot still around?

OnSIP.com also has a web interface that makes it differ from most of
these SIP servers. This allows you to see who is registered (presence)
and there's also an IM aspect I myself know little about. I believe
you can use a drag and drop approach to make calls via this web
interface, among registered users.

If you get on vuc.onsip.com you will need to register a SIP device or
software client to the SIP server (vuc.onsip.com) in order to make or
receive calls. Once registered, anyone can call your SIP URI, which
will be some...@vuc.onsip.com.

There are also four-digit extension numbers assigned to each user, so
if you have, say, a Polycom 650, you can dial the 4 digits.

OnSIP also allows the admin to set extensions for common SIP URI. For
example, if you dial 2009 on a device registered on vuc.onsip.com, you
will be effectively calling 200...@login.zipdx.com

If you are a VUC regular, or when you become one, please feel free to
email me and I will add you to the pbx on a "you want it done when?"
basis.

/r