The purpose of the Welcome Centre spec is to produce a 'first run' application which is displayed when the user first logs in to Ubuntu after installing it. This interests me because it makes documentation more visible to users, and should hopefully help people to answer their initial questions with the minimum of fuss. There have been several attempts at an implementation of something like this, but I don't think any of them hit the spot.
I decided to go with a slightly more general implementation. Welcome Centre, as I've imaginatively called it, is simply an HTML browser. 'Wow'. This should make it easy to design attractive, accessible first-run documentation for users, as you would design a website. But, as you'll see from the screenshot below, there's a twist.

Yep, Welcome Centre can run applications (and open documents, not just download them) at the click of a link. The code is very simple, but it should hopefully do the trick. It should also be useful for other tasks - some other use cases are covered in the documentation (just search in Yelp for 'welcome-centre').
This is the initial release, and it goes without saying that it might have horrible, horrible bugs:
Every last morsel of feedback you can offer is very greatly appreciated. Is this useful to anyone, for any purpose?