asterisk users - Apr 2005 - What software and types of connections are used by VOIP providers

I would like to start a discussion about real and big voip providers.
Lets say for example voicepulse or vonage or any other.

What software do they use?
Is anybody using asterisk?

What kind of connections they have to the internet?

What kind of equpment is used by them?

I hope that this group can be used for such a topic.
If not, please don't replay, or direct me to other groups.

Thanks

Bart,