When the weather is good i get out in the garden and give ds a little bucket and spade and he helps me do the weeding
We have a rock garden so we fill up empty juice containers with rocks and make lots of noise shaking them around. He loves the park and the swings and generally just being outside. If we can, we go to the lake and chase seagulls for hours. I'm lucky that ds doesnt put things in his mouth.

If its raining, we read lots of books. Sometimes if i feel like cleaning up a big mess afterwards we will do some baking together. Like if we make banana bread i'll let him stir it around and help with the ingredients but it is very very very messy (and fun!). I'll put on a cd and we will dance together and make silly faces. He loves his ball pit so we get in there and throw the balls all over the place. I do try to contain the mess to just one room when its raining as i feel like i cant escape it if i dont.
You could get a pkt of balloons and blow them up for something different.