One of the few things I was really hoping would be fixed in SP 2010 was the ability to have a navigation system that incorporated security-trimmed links from multiple site collections.
In SharePoint 2007, you can only have a common site navigation across a single site collection. As a site collection is the smallest possible database "bucket" you can store information in, you need to make sure that sites that will contain lots of content are located in their own site collection – which means if you have a team site generating lots of docs, images & / or videos (such as a training site) you have to fudge the menu system. Most people using an intranet or internet site expect to have a common menu system across a single hierarchy, so this restriction degrades the user experience.
Unfortunately this has not been improved upon in SP 2010, which is a real shame… but there is hope. In 2010, you can create your own service application. Using this architecture, it would be possible to create a custom Service Application called "Common Menu" that gets applied to the Web Application and replaces the existing menu system for all site collections within the web application with a common menu. I’m punching above my weight here though – I don’t know how to code, and this would require a bit of development. However, it would be a sellable product for a third party – which is part of the reason the designed the Sevice App architecture that way in the first place.
Some of the issues that would have to be overcome:
Ensure Security Trimming
How to make it efficient – cache with configurable timeout / rebuild cycle?
How to hook into security and site hierarchy changes – Site hierarchy ok, SP security ok, AD Security Groups much harder
How to disable it from inheriting within specific site collections (so you could still have an uncluttered menu system where people "work")
There’s probably others too…
Maybe we’ll see this widget come from someone like Bamboo Solutions? 🙂