You can use tumblr’s platform instead of wordpress.
First, you need to learn how to create a custom theme:
http://www.tumblr.com/docs/en/custom_themes
Then you can add David DeSandro’s neat, masonry API which allows you to control a whole bunch of properties. Though it is a Jquery plugin but not limited to wordpress, thus having the ability to adapt to any CMS / blogging platform. http://masonry.desandro.com/
Or,
if lazy, you can download a masonry looking theme on themefroest 🙂
Have fun.