Here's an in-game screenshot of the previous example (added some lights and set some texture maps to illustrate it better, this is not supposed to look cool):

@Chris: Yes, it's the same editor from The Orange Box. You can launch the editor by simply going into your steam app, choose the Tools' tab and run Source SDK - Orange Box in you case and click the Hammer icon.

See the work of Kasperg, who recreated Frank Lloyd Wright Kaufmann's House for the Valve's engine and did an impressive walkthrough video from inside the game (in this case, Half Life) which can be seen here:
http://www.youtube.com/watch?v=Tqsk4WARk2I

@remus: That would be great. I love TF2.

As for the workflow, you can't just export your geometry straight-foward to Hammer. You need your map to be modeled in a certain way:
All shapes must be created using grouped "boxes" of simple convex geometry (see http://en.wikipedia.org/wiki/Convex_set for convex geometry)
Complex geometry can be made from smaller pieces of this simple (convex) grouped geometry. No loose geometry is allowed. (I think I'll be using your ruby script, Chris )
I've made a quick example (I could post the .skp file but I don't know how to upload it to the forum):

Also, the whole map must be enclosed by a box, no gap, no spaces, an hermetic box made of convex geometry made of the same way I stated before, otherwise it won't work.

There are of course more things to know, I'm just giving an idea of the process.
Anyone willing to give it a try?

Hi!
Days ago Valve released an official exporter for Sketchup to their Hammer World Editor (http://l4d.com/blog/post.php?id=2510) --used in the development of such games as Half Life, Team Fortress and Left 4 Dead.
There was a thread covering an early unofficial exporter called PlayUpTools here:
http://www.sketchucation.com/forums/scf/viewtopic.php?f=80&t=11606&p=81001&hilit=valve#p81001

With this, gamers familiar with Sketchup should be able to create their own maps easily and (non-gamers also) could take the advantage of the game's engine to visualize their projects in a dynamic enviroment. Of course, one must own the game.

There's plenty of documentation on the Hammer World Editor out there. However little has been said about the Sketchup capabilities/tips/workflow in the process of making a level for the Valve's engine. Let's see if we can get this moving by sharing our experience. Can we begin, please?