The little bit just decided today that she can sit up unassisted.  We have worked on it a little but she hasn't been very interested.  This girl LOVES to be on her tummy.  She has never been mad about tummy time.  She has always been so content laying on her belly and playing.  So sitting up just wasn't a priority for her.  But it was another amazing weather day so we took a blanket out front and a few toys to enjoy the day and wait for Dean to get home from work.  I decided we should work on sitting so I plopped her down and that was it.  She just stayed.  She was able to catch her balance and readjust and even got down to on her belly without just tumping over.  I was impressed.  Growing, learning, changing.  Everyday.