Posterous allows you to run your blogs in a custom domain and I was using this recently for one of my sites. Posterous also allows you to customize the look and feel of your blogs through their admin interface so that you can blend it well with your site.

One major pain point with Posterous was that they have these annoying drop downs which prompt people to sign up for Posterous when you hover over the title area. This is ok if you are running your blog in Posterous domain but it becomes intrusive when you use it for your own custom domains. So, I used firebug to find out the ids of these drop downs and added a display none in the HTML customization area of Posterous for these ids.

#posterous_required_header { display:none; }
#posterous_bar { display:none; }