Not to say that I didn't find solutions for this as QuickTopic does a great job of it, and Movable Type or any standard blogging tool where you have knowledge and control over templates set up can be easily adapted to this task.
But outside of QuickTopic, blogging tools are not really designed to send out invitations nor to provide a comprehensive notification system to discussion participants.
You say I should use a forum?
Yes, I have tried that one too, but generally forum services and software are well geared to support communities where multiple topics are discussed, have little in the way of invitation tools, don't often integrate RSS feeds for distribution, and are most generally not very professional looking (lots of features, icons and grid lines, but that is not what I really need).
What I really want is a tool that allows to start a web-based conversation where:
- access and ease of use are given max priority
- anyone can participate no matter what computers they have
- there is no software to install
- the system works across all browsers
- I can choose to make my conversation public or private
- participants can subscribe via RSS or email
- I can watch live the conversation as it unfolds
- It's free to use
