Try Open Studio http://draw.artcontext.net/cgi/index.cgi?lang=english of http://artcontext.com/
You can interactively (alone or together) create your masterpiece and save it on their server. Of course, you can reload it at a later time :-)
On load, the painting process is recovered as a movie. I think, it is even more interesting as the old MetaBaby.
Don't forget to have a glance at the philosophy behind: http://artcontext.net/crit/museums/cur_al.html What they are striving for, is a graphical Wiki.
There are so many Wiki-like passages in the article, that I give a link to the CritOrg'ed version for annotating in context: http://crit.org/http://artcontext.net/crit/museums/cur_al.html
The Open Studio project is one of the most interesting collaborative ideas I've seen recently. Indeed, I started to write that most of the contributions were junk, but after another look I'm not so sure. Many of the files I opened at random had at least one section that I'd consider real "art". Perhaps this studio could be considered as "primitive" Internet-collaborative art--they reminded me strongly of the famous cave-drawings.
Perhaps someday even this text will seem similarly primitive, if humanity (or its descendants) progress to far better means of communication. --CliffordAdams