I had a quick rummage in the cupboards, and found some lovely thick zip-lock bags we'd picked up at the farmers market. Inspired by other posts I've seen, I filled one bag with fingerpaint, and stuck it to our glass dining table with sellotape. Indy loved it, and it was nice and easy, mess-free fun (hurrah!).
He loved it so much, I wanted it to continue, so I found another zip-lock bag and filled it with glitter and water, and taped them to a tray so he could play with them in the living room. He was captivated! He loved squidging the two bags at the same time, feeling the contrast between them, and seeing the colours mix. This is a definite one to repeat, he loved it so much he tried biting them both several times (do they ever get over the 'putting everything in their mouth' stage?).