Unfortunately, a group of hackers were able to successfully gain root access to the server(s) hosting the Ubuntu Forums today and compromise the entire website. The Canonical IS team is investigating the issue as we speak. The attackers replaced the website with the following image:
Unfortunately, it appears that all usernames, password hashes, email addresses, and personal information was available to the attackers. Although plaintext passwords were never stored in the database, users are still strongly encouraged to change their passwords anywhere that they have used the same password.
In the meantime, if you visit the Ubuntu Forums website, you will be greeted with a message explaining the current status of the incident. There is currently no estimate on when the site will be back up and running. When this happens, users will likely be forced to change their passwords.
There are 3 excellent resources you can make use of while you're waiting for everything to come back up. (In fact, you should already be using the first one!)
Download the official 2buntu app for both Android and Ubuntu Touch.