Diego can sit up pretty much on his own now. You have to put him in position and he can stay like that indefinitely. He will lean over and play with toys on the floor and everything. He still falls over sometimes if he tries to reach for something a little too far away. He has yet to put himself in sitting position but it really looks like he's close to it.
I read in a baby magazine that his getting on all fours and rocking is supposed to happen around 7 months and he's been doing that for weeks now! Maybe he'll be walking at 8 months like I was.