http://wiki.apache.org/geronimo/RoadMap
It breaks down functionality from the user's point of view and has a graphical status indicator next to each feature to show whether it's supported, partially supported or not yet implemented.
Of course, right now this information is not very accurate, since I'm not sure of the current state of many of the listed features. It would be very helpful if active developers could look it over, fix anything that's wrong, and add anything that's missing. The level of detail is somewhat arbitrary, so feel free to add more features to the list where appropriate.
Cheers, Erin
