Though revision graphs are not a feature of Subversion, they are very useful for big projects.
I'm publishing revision graphs for the public hugest repositories around the World. Like KDE (+1 million of revisions) and Apache (near) which are already available.
So far, people needed to download the full history of the repository wasting a lot of time and a considerable space on disk. Now, this is not necessary because they are instantly available on the Web.
If you know a huge public Subversion repository (nor Apache and nor KDE) then, please, reply this post adding the public URL and I'll publish it.
Please, keep in mind that this is quite experimental at the moment. Revision graphs, plus other features like statistics and so on can also be viewed.
Thanks in advanced,