Remember the "12 Days Of Portal" song we did last year?
It's recently been included as a part of Goodbye Christmas Caroline, a collection of fan made Portal themed Christmas carols. It's great to see a lot of talented fans coming together to create something like this, and there's a lot of effort been put in by all involved. At the moment, we're particularly taken with This Is Aperture, but that could just be because it's the one that's most recently been finished.
Several of the songs still need work, so if you're interested in contributing, drop by the project's thread on the Steam forums and say hi.