Seth Godin keeps a running total, based on AlexaÂ data.
On a related note, Search Engine Journal has an excellent article about Yahoo’s acquisition of MyBlogLog:
“MyBlogLog is a hybrid between a blog analytics solution and a social networking environment which has recently swept the blogging world by storm. A â€˜MySpace for bloggersâ€™, MyBlogLog lets registered members congregate around communities set up by those members or the blog owners themselves“
MyBlogLog was #47 on Seths chart.