As I said two posts back we use the Community Edition of SugarCRM as our Customer Relationship Management system. SugarCRM is very good and it has a good community behind it. There have been a lot of modules written that extend SugarCRM in various ways, many of which interact with other online systems. I have added a couple to our install of SugarCRM recently. They are connectors that allow interaction with Dimdim and Google Calendars.
Lisa and I recently hosted a small online meeting using DimDim. DimDim is an Open Source web conferencing tool. As with all open source software it is freely available for use. In fact, the DimDim people go a step further and will allow you to host conferences using their software on their website for free.