A similar idea has been meandering around my biscuit box for a while too, or rather I was thinking about a quite widely scoped collaborative creative project involving (and also probably leading up to) an "event", and that would result in a publication of some sort released under a Creative Commons style license.
Whilst I absolutely agree that it should be a non-profity venture I'm not so sure it would be easy to make such a thing generate money for charity. Alternatively, if you had an "event" associated with the process of creating the "thing" you could probably use that to generate money for charity a little more easily.
One of the reasons I haven't tossed my idea out into the arena yet is because it's hard to put a scope on a project like this.
The way my thoughts were leading was actually that there would simply be a "theme", such as a place and a time (real or imaginary), with contributors able to freely add content of whatever type (prose, game settings, art, design, animation, film, poetry, theatre, sculture, creatures, clothing, artifacts, music, comicbook art, you name it). I was thinking that the final product would be more likely to be a CDROM or DVD containing multimedia content.
I'd envisage the "events" to consist of a short series of workshops culminating in an "exhibition"...erm...call it a "con" if you like, but the "con"tent would be drawn from a broader range of sources than a traditional con.
Now I don't know if anyone else is interested in anything like this, but I certainly would be.
As far as I can tell there aren't THAT many people around who'd be serious about contributing to something like this anyway (not at the long term level of commitment required to see the project through anyway), so perhaps you'd actually have to run this as a "sub-event" at other cons. [shrug] I dunno, detail thrashing required aplenty.