Emma Rose is a little bit older than 18 months, but at the age you're talking about, here are some of the things she liked to do (and mostly still does!):

• Colour with crayons -- I got a giant pad of paper and some washable crayons and she'll scribble away
• Finger paint on newspaper outside or finger paint in the bathtub (naked, of course, for easy washing up!)
• Water play inside -- I filled up the baby bath with water and put it on the kitchen floor on a big towel, and let her go for it
• Musical instruments -- we've got heaps of maracas, cymbals, drums, plastic guitars, etc (and a nice pair of ear plugs for me!)
• Squishing homemade play-dough -- I make it with lots of salt so she's not tempted to eat it! (The look on her face when she tastes it is priceless, though!)
• Playing in a tent -- I used to take all the chairs away and hang a huge quilt over the dining room table, and she'd crawl in and out, take her toys and the dog in there, and hang out for ages, playing peek-a-boo when she wanted to know I was still around. Eventually we got her a child-sized tent and put it in the living room so she can go in and out whenever she wants
• "Helping" with the laundry -- she loves taking the clothes out of the laundry basket and then putting them back in, so I used to get all the clean tea towels in a laundry basket and just let her go wild