DD2 is army crawling. My earliest yet - she's not even 6 months old. She will push herself forward while on her belly, with her feet and arms. I watched her get to a toy five feet in front of her.
I think she learned that if she's going to survive around here she needs to know how to move herself away from older siblings quickly.
Re: Mobile baby season has begun in my house!
DS1: Quinn - 10.22.10 and DS2: Cole - 01.18.13