The whole navigation when on your blog seems confusing. If you click on the logo while on the blog, you get the blog home, but if you click the about link, you are taken to the main site with similar navigation (and a similar looking logo/layout). You really don't get the feeling that you've left the blog site.
Wouldn't it be simpler and much more straightforward to just add a blog link to both your blog and your main site, make your blog look like your main site and make the logo link to your main site. After all, isn't your blog part of your main site?
Also, when you click on your profile link on the right of your blog you get a posterous profile page. Seems like that should link to the about page as well.