Mads Kristensen posted an article about an HttpModule to move ViewState to the bottom of the page. It's based on Scott Hanselman's similar blog post.

The nice thing about moving ViewState to the bottom of the page is spiders don't have to sift through it, which means potentially better spidering and search engine ranking. Another benefit is that your page may render faster on browsers since more of the visible HTML is retrieved sooner.

I like the idea of making an HttpModule out of it, because then you don't have to have a custom Page class or anything .. you can just drop the HttpModule into any project & it starts working. Assuming it doesn't have huge bugs, of course. :)