Nowadays, a PHP based CMS is the de-facto standard if you want to publish online content, and it's easy to understand why when one checks web hosting offers around: it's the most widely available option and the easiest way to deploy web solutions. However, when site performance becomes a crucial issue, one might want to explore alternative options. Lately, I've been starting looking towards Python web frameworks (and more specifically Django), but there are of course plenty of others options as well.
Why not give a try to Zotonic, an open source CMS written in Erlang? Erlang you say? Yes, Erlang, a programming language created by Ericsson (they make mobile phones as well) and designed to create distributed, fault-tolerant, and real-time applications. It means that of course, Zotonic benefits from the language features mentioned above, making it a very interesting solution for high-load websites.
Here are the keys features:
Some screenshots of the front-end and a screencast showing the administration interface:
In conclusion, Zotonic is a very promising CMS even if it is still a young project and as such, lacks maturity and a wide user community. However, I encourage you to give it a try, just for the sake of experimenting with new solutions: I'm convinced Zotonic popularity will rise over time.
Project site: http://zotonic.com