DimDim
Important:
Dimdim has been acquired by salesforce.com. Your free Dimdim account will remain active until March 15, 2011. After that date, you will no longer be able to access your free Dimdim account.
Salesforce has provided a FAQ page for information regarding the impact of the takeover. It can be found here.
It is important to know that any saved meeting content or documents will not be available for download after March 15, 2011. Details on saving your content can be found through the FAQ.
Overview of DimDim
Step by step instructions on Getting Started