My 15 month old had lots of fun with paint today.
I bought some cheap kids water paint and a pack of a4 card. Stipped LO down to her vest and then we went into the kitchen (door closed) and I laid out about 10 sheet of card on the floor and got a tray and put splodges of different coloured paint. I gave LO a couple of spoons etc. to dip in it. More of it went on the floor than card though! I put it on LOs hands/feet and helped her stamp feetprints on the card and make handprints/wipe her hands on it and we put splodges of paint on the card and I helped LO rub it in. It was great fun and now we have about 8 pictures to hand out to friends/family. Afterwards my kitchen was covered in paint though - it took me an hour to scrub it off the floor/cupboards and fridge and half an hour to scrub LO in the bath! Be warned she ate a few mouthfuls of paint though and then had a horrendous nappy about an hour later!
We also have some old containers - LO likes it when I fill one with pasta (dry, uncooked), one with water etc. and she likes to shake them etc.
Walks are great too. I take her round the park without the pushchair and we stop and look at everything - grass, flowers, drains, sticks etc. A 10minute walk takes an hour!
I'm going to try some "messy play" too with a container of cornflour and one of water and let LO pour and mix them to her hearts content.