i've done 4 sites with phpNuke and NukeEvolution and I have to say that I'm still amazed by the flexibility of nuke. i also run 2 other sites off wordpress.
Custom.. ACMS Current version on site has a few errors because I quickly took some things offline because of spam.. new version to be up within a few days
I currently have several websites and use Joomla and Wordpress. I think Wordpress has some of the best looking templates around.
I'm using Wordpress IPB PHPBB SMF Joomal However each sites has its own needs and you should not use what others are using, instead look out for a CMS which best fits your need. You can get many CMS with demos at hotscripts [dot] com >> PHP >> Scripts
I used to use Joomla, love it. It's so damn powerful, but the draw back is it requires alot of resources. It's not great SEO wise default, but with URL rewrite and the SEO patch it actually does incredibly well (providing you understand SEO and set up your sections/categories correctly), it can work like a charm. The only other possible downside is that you are forced to have tables in your layout in certain areas. I modified Joomla and offered a patch which completely gets rid of those tables and converts headline contentheading spans/divs into H1 tags, etc, which is also great for SEO. it's in Joomla forums under custom development.
I currently have Drupal, Joomla and e107 and some board software along with a creative commons host running. Not counting WP.