2 posts in a day!
At 5 months old, my son whom I need a new nickname for, has made some significant developmental progress.
Size-wise: 16.4lbs, 25" long, 16" head circumference, by my measurements.
Mobility: He can roll everywhichway and scoot about in circles and futilely kick his legs above the ground while on his tummy in a hilariously unsuccessful attempt at moving anywhere at all.
Socially: He's kinda shy. If you amuse him, he'll smile and squeal for you, but if you do too much, he'll present you with the biggest frown of babyland, followed a minute later by large amounts of crying until he's back in a safety zone (i.e. mommy or daddy holding him against our shoulders while walking around). Most likely he'll just stare at you though.
Vocally: No talking yet (ha ha ha), lots of noises, and his favorite word to listen to is Banana so his mommy sings it to him to various tunes throughout the day. You should try it sometime. "Banana banana baaanaaanaaaa."
He still loves standing up (with us helping hold him up). He can sit up for several seconds unassisted (he made it to 20 seconds the other day!). He loves it when people applaud his efforts. He likes to sleep with his bum in the air occasionally. He caught his first serious cold and is very snuffly right now. He's back down to usually only waking up twice a night. He's getting quite good at eating rice cereal, though it still gets EVERYWHERE because he wants to feed himself and is constantly trying to grab the spoon. He's discovered that if he kicks in the bathtub it splashes, which has made bathtime more exciting (am I a bad mom for not bathing him daily? He doesn't honestly seem to need it every day, a couple times a week keeps him smelling nice and looking clean and healthy).
Next up on the milestone list: Sitting for several minutes unassisted. Holding himself up in a standing position. Eating baby food (I want a food processor). Crawling. Sleeping through the night?