“Most parliaments (80 %) now use at least one open source application. In most cases this type of software is used to run servers (50 %), for webpublishing (36 %), databases (31 %) and email (31 %).”
Well, that’s a start. Document-management and content-management systems were growing most rapidly as e-governments made more/better use of the web. I recommend parliaments use Debian GNU/Linux. It has tools for the web, the server, the database or the client systems of you IT. There is no cripple-ware. It’s all Free Software and you get to run it on whatever you want the way you want and it’s $0. Just install it and run it.