Although I have seen and evaluated PHP Website", I haven't seen see Liferay, which is equally -- perhaps more -- impressive.
I signed up for the demo site, and was greatly impressed by the elegant interface, modular architecture, and existing functionality.
I'm also always impressed by companies -- life Liferay -- that build a successful business around open source software.
Follow-up: Shortly after this post appeared Jordan Anderson, a Master of Urban Planning candidate at New York University emailed to comment on my post, and related CMSes:
I've been reading your Planetizen TechTalk posts on using open source content management systems as platforms for local government information sharing. As a current urban planning student and former technology professional, I share your enthusiasm and wanted to mention I've been very happy with the PostNuke system and community.
Early this year, I used PostNuke to centralize information about Helena, Montana's downtown redevelopment. For my capstone/thesis, I'm working on a more ambitious project (requiring serious PostNuke hacking) to put together a portal for urban planning information in New York. Read about it on my project blog, and in a short overview document [360K PDF].
And you probably know about the e-democracy-oriented CMS, CivicSpace--a Drupal variant.
Thanks for the wealth of information, Jordan!