I posted about Project Euler being down a few days ago. It’s back up, but only as a static site. So you can read the problems, but there’s no access to the functionality for checking solutions, or getting into the solution forums, or anything like that. There’s a thread on reddit about this, apparently created by one of the Euler admins. It does sound like they are going to get full functionality back up and running at some point, though they don’t seem at all sure about when that will be.
I’m actually not working on any Euler problems right now, but I had intended on getting back into it at some point. Project Euler is such a great resource, I really hope they can get it back up and running soon!