What is a good tool for Build Pipelines?
Edit (03/2018)
Since writing this question in 2012 and answering it in 2014, numerous tools have come online to support what I originally wanted. Jenkins now supports scripted pipelines natively and has an excellent UI (Blue Ocean) for rendering them. Those stumbling on this question should consider using these for their pipeline needs.
End edit
(Old answer)
It didn't exist when I asked the question, but Jenkins' Build Flow Plugin does exactly what I needed, and creates pipeline views very well.
https://wiki.jenkins-ci.org/display/JENKINS/Build+Flow+Plugin
You could use Go if you used a dummy material (an empty git repo, for example), and then used the API to trigger a pipeline and upload artifacts.
But, that's quite some effort, and you should probably only do that if you have a very good reason otherwise to use Go.