Nice to see that Headshift have got the new Demos site live. This was the last site I worked on at Headshift, and there's quite a few aspecs to it of which I - and m'former colleagues Neil Roberts and Andy Birchall - feel quite proud.
It's architected with the "Everything-is-a-Item" approach that I learned from my Headshift predecessor, erstwhile colleague and all-round-good-egg Matt Perdeaux, which opens a lot of doors in terms of code reuse and making the most of your content.
Put simply, everything on the site - blog posts, comments, people, users, CMS pages - has the basic common data such as title, summary, and full description abstracted to an Items table, to which you can join as required in your SQL. All links between items and other entities (e.g. tags) are done at the Items level. This makes things like a global search across all content trivially easy (at least in theory - doesn't always work out that way of course... ) and means that once you've implemented tagging for, say, blog posts, you can have tagging on everything else as well with virtually zero extra effort - because everything is-a Item.
As with a lot of systems I've written over the years, it gets a little frustrating that some of the nicest bits are hidden away from public view in the admin interfaces. But you'll just have to take my word for it that there are lots of self-contained AJAX-driven custom tags that do things like tag administration and item-to-item linkages, which only had to be written once, and could be brought into any form for any kind of item and would work straight away - because everything is-a Item.
Other aspects of the site which give me that warm fluffy feeling inside include the friendly url scheme. The site is written with a Fusebox front-end, but there's a very thin layer above that which translates human-friendly urls into fusebox-friendly urls. This is done with Apache mod_rewrite, translating a url like
projects.cfm then parses the sParams string into its expected parameters, retrieves any referenced items into request scope, checks permissions, works out the appropriate fuseaction, and passes on to the FB framework by including index.cfm.
It would make a good CFUG case study, I reckon. (Hey Matt - fancy another vaudevillian double-act? Gaw blimey, roll out the barrel guvnor...) Mind you, I'm not sure if it's appropriate for me to reveal the technical innards of a system when I don't work for the company anymore... hmm... over to you then Neil ;)