I'm on my second batch, and decided to ferment in the carboy, so I could watch. It's on day 3 fermenting, I've got a nice thick krausen (needed a blowoff tube). However, I noticed it seems like it's 'raining' sediment from the krausen. It basically looks like globs of what eventually ends up as the yeast cake, falling down from the top. Is this normal, or did my wort get infected somehow?
It looks like yeast cake because that is what it is. The yeast clumps together, and settles to the bottom as gets near the terminal gravity. That is called "flocculation", and some strains are much more prone to it than others. If you go to the manufacturers web site, they usually give a rating: low, medium or high. With the high ones, sometimes it is beneficial to rock your carboy and swirl the fermenting wort to bring some of the yeast back into suspension. This is called "rousing" the yeast. (Obviously you want to be very careful handling glass carboys, so don't get too enthusiatic). If the yeast drops out too quickly, the beer may be underattenuated.