This forum supports both http and https: http://forum.ethereum.org/https://forum.ethereum.org/
The http version should automatically redirect to the https version. Why? Because if someone is on a public WIFI network (library, airport, whatever) and types forum.ethereum.org into their browser, and logs in, then their username/password could be trivially stolen by anyone else on the network.
Looks like the forum is running on nginx. If you need an example https redirect config just let me know.