So far I've built all of my client sites using Wordpress. Mostly cause it's easy and the user community is huge. I can type most questions into the google machine and the first couple entires are all blogs with a post that is either the answer to my question or close enough that I can then figure it out. But, as of late I've been bumping into the limitations of Wordpress more and more. And I find that many parts of it are over developed and I feel they are trying to shield theme developers of having to know much about the architecture.
In short, I've got a new project from a new client and I'd like to try something new. I'm willing to try any of the packages that WebFaction supports and may be willing to install something using a custom script (Pyramid anyone?). The site I'll be building is going to be an information resource and blog about a specific topic. If we get enough traffic from the content then the client would like to build a store out the site and sell products related to the topic. He has a number of topics and domains he'd like to try out so I see this code base being reused as well. I don't think I'd like to host ecommerce part of the site, but rather use shopify or yahoo stores, unless someone convinces me otherwise.
I know this may sound like a "do my research!" question. I'm already leading towards Django or Pyramid, but if there are some fans of Drupal or Joomla who see those as better solutions I'm all ears. I'm really only interested in learning a new tool and having some fun with it.
I second the Django recommendation. I'm not a particularly advanced developer, but my work in Django has completely changed my perspective of what is possible, while creating a level of ease and enjoyment I hadn't known with PHP (surprise...)
The development server and stock admin interface is particularly effective. The documentation is amazing, and the IRC community is very active and helpful
For blog type stuff, maybe have a poke around http://blog.montylounge.com/2010/02/10/eleven-django-blog-engines-you-should-know/ It's a bit old but most of the projects are still maintained. When I was first checking out Django I rooted around the project directories for hours checking out the different methods