http://content.open-ra.org will end it's life on the 1st of June 2014. Please download everything you need from there in advance. There will be stored backup just in case. Contact me if you need something from that site in future.
New site ( http://resource.openra.net ) does not support Units and stuff so far, but it's already a primary platform&service for maps which OpenRA already uses and where all the support is concentrated on. Follow https://github.com/OpenRA/OpenRA-Resources to keep up with updates of OpenRA Resource Center.