Well, we've been waiting for some definitive first words from Mudpuppy -- he doesn't really enunciate anything quite so clearly yet, but he has definitely begun to repeat some sounds that he associates with certain situations.
"Da da" -- when he first started saying it, this was more of a random babble; now, I think he associates that word with me, partly thanks to the encouragement of others in the family.
"There he is!" -- He will consistently repeat this phrase after we use it. We say it when we're pulling on a shirt: "Where's [Mudpuppy]? Oh -- there he is!" And he'll laugh and laugh and say something that sounds sort of like "der e iz." It's pretty consistent, so we don't think we're imagining it, but I think we'd be the only ones to recognize it as a phrase.
"Alleluia" -- He definitely says this word, and pretty clearly at times, too. We often work a sung alleluia into our family prayer, and his face lights up when we sing it. Once it sounded like he was trying to imitate it a few months ago, the kids and I jumped on it, and have been saying it to him repeatedly ever since. "Say 'alleluia!'" So, now, he does.
He clearly understands many words as well -- banana, eat, drink, mama, and the names of his siblings. His face lights up when I mention his siblings' names -- for instance, when we're getting in the car to pick them up, I might say, "Should we go get [Bear]? And [Mouse]? And [Jaybird]?" And he will smile and his eyes light up for each one; he'll look off to the side to see if they're around.