From Microsoft's Family.Show's discussion boards, I discovered Geni.com, a Flash based online family networking site. It allows you to build your family tree in a collaborative way (that is to invite family members, and let them make addition and modification to the tree). It is a great site, with a simple (if not so good as Family.show) UI.
Have a look here.
I have now a tree that includes a total of 500 people (not directly linked to me) included on the tree.
There are some security concerns about the site that I am going to discuss in future posts.