Joe & Sally like WordPress
I'm jumping ahead a bit here, but I thought I'd go ahead and mention my favorite blogging platform: WordPress. WordPress is built on PHP and MySQL, so you will need a hosting plan for your site that supports both these systems, but WordPress itself is free, highly customizable, and prides itself on it's famous 5 minute installation. Even better, there is a very active community behind the product and a lot of WordPress users are Mac OS X-savvy.
There are a slew of available templates for WordPress, and if you want to design your own template, then you'll probably be interested in dissecting one of the default themes. If you've been running your blog on Blogger and want to try to switch to WordPress, there's a tutorial on how to accomplish this. Some people have adapted WordPress as a personal information manager, and it is possible to create a local installation on your Mac to testflight changes before updating the publicly hosted version. I run my personal site on WordPress and absolutely love it. Give it a shot.