Son is in 1st grade now, but here are some of our B4 1st grade stuff, and summer stuff we do....there is more, but I'll stick to the "free" stuff (if it requires supplies, it isn't very free...right?)
Computer games on sites I agree to - the computer and web access are already paid for.
Ton's of art stuff....I always have paper, paints, crayons, pencils, etc on hand. Probably too much, both of my parents were art majors, so you can guess what a lot of Christmas and birthday gifts have included over the years for the kids.
Turn on the radio or put in a CD and DANCE!!!!!!! (keeps moms in shape too). And when he was tired, I would hold him and slow dance in circles to Brother IZ (Hawiian musician, passed away a while ago, he did that modern rendition of "Somewhere over the Rainbow" that you often hear on commercials now. His voice is beyond words.)
Savenger hunt nature stuff at parks and outside of the house. Glue them to paper to make your own "nature" collages later. I know...more art, but then you only pay for the paper and the glue (This is a great thing to do with pressing flower in books).
Hit anything baseball in the back yard....crumpled tin foil, paper, whatever you can find, and a stick. Make bases out of things like pot holders and plastic container tops.
Reading before naps....we did a lot of it! All 3 kids!
All of my kids also had to be a part of the chores as soon as they understood words well. Setting the table, making their beds, helping with shopping and putting away items....and that consumed plenty of time. I was and am still the TASK MISTRESS of this home! That takes up some of the days time on it's own.
On sick days, I admit we'd turn on the TV and vedge out together after I was done getting the rest of the work around the house done. I'd use the TV as insentive to get pedialite, Yogurt, diluted juice, apple sauce, rice, etc down.
Oh! And when my son begins being wild and running around the house, breakingthings, hurting himself, getting BOY CRAZY, it's time to take it outside, I've even told him to go run aroun the house 5 times...he usually comes up with something creative to play by the 2nd loop.
If you can't get outside, go back to the dancing thing.
I even had kids exercise videos on hand for when I needed to wear them out.