Here's an activity that, like pool in the kitchen, worked for us for quite a few of the early toddler months. Now that they boys are hitting 18 months, I find that their new skill of gleefully throwing things (especially rice and sand) prevent us from bringing out the rice play, but it was great up until just a couple of weeks ago.
Setup: I bought a 25-pound bag of the cheapest rice I could find at our local Asian market, and used about half for this activity. I just dragged our plastic pool in from the garage and set if on the kitchen floor on top of a large sheet. Then I dumped the rice inside and gave the boys a number of bowls, spatulas, and other pouring objects. I resigned myself to them eating the rice, and over the course of playing with this many times, I didn't notice any resulting tummy troubles.
When the boys are done, I put them in their high chairs so I can clean up without them under foot. I pour the rice into a plastic tub and store it in the garage for future play.
Now that the boys are so steady on their feet, a nice sand table would be perfect for rice play indoors, though I'm quite sure it would still involve the thrill of throwing and pouring the rice on the floor. It's a great activity, though, and keeps them occupied for up to 20 minutes.
Note: right before I got our sandbox, I did try doing this outside a few times, but it was kind of a pain. Twice I forgot to sweep up the rice in our haste to get into the house, and both times it rained, making it much harder to clean up.