I tried accessing the main site several times today from about 8 PM to midnight (EST).
Rather than load a page, my browser (Firefox 2.0.0.13) was prompting me to save or run an application loaded from the site. All Project Euler-related sites seemed to be down as well, so I couldn't find a good place to notify admins of the problem. While I hope it was just a freak occurance local to my computer, I figured that I should mention it. It's definitely a symptom of an attack on Project Euler, but simply being a user puts me in no place to diagnose such an issue.