CKAN is the software we at Liip used to build opendata.swiss, Open Data Zürich and the Open Research Data Platform Switzerland. It's written in Python (based on Pylons but currently being migrated to Flask). CKAN is open source, of course, extensible, has a great community and is a pleasure to work with, and I wanted to share that with my coworkers, who mostly program in PHP.
This talk is now a couple of years old so technical details may be outdated, but I hope it still conveys my enthusiasm for Open Data and for CKAN.
Here's the video and my slides.