2 weeks ago, Alastair was fairly immobile. Sure, he could roll around and eventually get near where he wanted to be, but aside from some military-style elbow-crawling, he would pretty much stay where you put him.
About a week ago, he just got up and started crawling. No real catalyst or anything: apparently he just decided it was time to be mobile.
Then on Thursday, Amanda called and told me that Alastair had stood up in his crib and knocked the monitor into the floor. This was a first, but for the rest of the day, he stood up wherever he was. I lowered the crib when I got home, to keep him from pitching over the side, but he's undeterred. He's standing half the time we go in to get him up, and he's started motoring around on his feet inside the crib.
He'll take steps across the den floor (provided you're holding him), and took a nasty tumble when he stepped off the rug in his socks last night.
Finally, it seems he's getting interested in learning to speak. Amanda had him in her lap on Saturday, and Vivienne jumped up into my lap. He looked at her and shouted something that sounded for all the world like "kitty!". Later that night, his grandmommy was watching him, and she handed him his stuffed duck. He shouted "duh", or something very much like it. When I enter the room, he sometimes says "da da... dadadadadadada" (of course, he also sits around and mutters this when he's playing, so I'm probably reading too much into that one).
In short, the kids picking up skills like crazy, and treating them as if he'd been doing them for months already. I think he waits for Amanda to leave the room, then jumps up and runs around practicing all his advanced maneuvers.