We were offline for about an hour on Sunday morning around 5AM or 6AM PST. We were bringing a new server online...it wasn't supposed to take the primary server offline, but there was a mixup at the hosting provider regarding IP addresses. We ordinarily notify a few hours in advance of scheduled maintenance in our news forum.
I also post to Twitter @virtualmin whenever we have unscheduled downtime.
Don't worry, though, we're not going anywhere; if you ever find us offline, you can be sure we'll be back in a few minutes. We're also in the midst of adding full redundancy for the software repositories...so even if the website is offline (scheduled or otherwise), installations and updates will continue to work.