There appears to be connection problems going around as multiple people are unable to log in tonight, including multiple tipsters and yours truly. It's definitely a widespread problem, as the Blizzard Tech Support team is currently asking for ISP and tracert information over on the official forums while they try to track it down.
While some people are positing that this is a merged battle.net account problem, it's worth noting that we also know of many people, including a couple of our bloggers, are still able to log in fine with a battle.net account. At the same time, some posters in the aforementioned thread are saying that they can log on fine when they use an unmerged pre-battle.net account from a family member or roommate.
Once we get a clearer idea of what the problem is or when it's been fixed, we'll let you know.
UPDATE, 10:30 PM EST: Okay, This is Daniel again, and I can log on with a battle.net account. This is the same one that wasn't working not 10 minutes ago, for the record.
UPDATE, 11 PM EST: It looks everything is working fine again. Play on!