On the 24th of July, Smashing Magazine did a study on blogs.
You can read it here: http://www.smashingmagazine.com/2008/07/24/a-small-study-of-big-blogs/
It is a quite interesting article, and definetly worth a read, but in the comments I found an even more interesting thing. Leon Paternoster (of leonpaternoster.com) made a layout that incorporated all the research into one template.
You can find it here: http://leonpaternoster.com/blog/2008/07/smashing-magazines-ideal-blog-layout/
Mod Edit: Moved to The Lounge.