Yes! Sometimes I feel I'm the only one in my crowd who does this, although my kid just finished prek. My kid is 5 and will start kindergarten this month. He met all the requirements to start K like letter and number recognition, counting to 100, etc (except tying his shoes) so I just bought a bunch of Kindergarten workbooks at ToysRUs and am having him go through a page or two a day in each book - thinking skills, hidden pictures and even dot-to-dot and mazes so he could practice writing small lines.
He practices writing his name every day and the names of his friends, and reads a book or two to me every day. He is trying to write short sentences on his own "I like dogs. I am cold."
We listen to music and he either claps along or we grab somethig that makes noise and he follows the beat. We also make up songs (like Winnie the Pooh does!) so he is learning to rhyme and put words to tunes.
I make him draw or color, only to help him to learn to stay in the lines or to picture something and being able to draw it.
I used to be a big nazi about no screen time (tv, video games, computers, ds) during the week but after learning he will be in a computer class at school, I started having him log on to PBSkids.org or Disneyjr.com and playing around on it this summer.
We do this after bfast each day (if we have time), or before he wants to play. It takes about an hour. He loves it. I always give him a choice and most days he wants to do school. I think my kid is one of those kids who need constant stimulation and challenges so I have to do whatever I can to keep up w/him. I am really proud of him and grateful that he doesn't complain. In return, I let him let loose after we do school and try not to ask too much of him during the summer.