Vyew
Vyew (http://vyew.com/) is a free, Flash-based collaboration platform, suitable for small group work and light weight online conferencing. Consisting of text chat and whiteboard, with optional phone conferencing (toll charges apply), you can share presentations, images, and screenshots. A new feature is a desktop view. Meeting rooms can be created on the fly, even using the guest login. Participants can be invited by email or by providing the meeting room number. Participants can be desginated as viewers (view only) or presenters (full options.)
Registration includes file storage space, so that files can be viewed, edited, annotated and shared. Without registration, only the chat, image sharing from online libraries (Flickr, etc.), drawing pad, and phone conferencing systems can be used. Unregistered users can save images to their computers. Vyew is in beta and the business model is not set yet, but they do promise two years of free services for those who register during the beta period.
Vyew requires Flash and Java 1.4 plug-ins, and has been tested on Internet Explorer (5.5+ for Windows), Firefox (1.4+ for Windows), and Safari (for Mac).
The Vyew website has a good explanatory screenshot.