I don't know where they determined the entries on this list, but I'm 100% sure that A List Apart is running on PHP/MySQL via the ExpressionEngine CMS (http://www.expressionengine.com)... which then makes me wonder how credible the other entries are.

Edit: I did a little digging and it looks like they used to be on RoR but switched over sometime in mid '09... so I guess that explains the mistake.