Wasn't I talking about fermentation being awesome yesterday?
Not 6 hours later, the Belgian Strong (pictured below - and this is the inside of my temperature controlled freezer) started producing major amounts of CO2. The foam at the top that gets created is a byproduct of the fermentation process and it's called krauzen (pronounced "kroy-zen"). The Harvest Blueberry is still doing its thing below, but doesn't have much of a krauzen head at the moment - typically, the first part of fermentation (called primary fermentation) is when the yeast have themselves a couple of all-day/all-night parties. Right now, the Blueberry is in its secondary phase of fermentation, and the remaining yeast are a little tired and don't work as hard (slackers).
With big beers (like the Belgian), the krauzen can get so intense that you need a blow-off setup so you don't end up with yet another mess to clean up.
As many times as I've seen fermentation happening live, I still can't help but be amazed and intrigued at the process.