I really like The Preschooler's Busy Book by Trish Kuffner. I've mentioned it before, but this is my official recommendation. I know that means a lot. I like, first of all, that she is honest about being crazy at home with multiple small children. Then she offers planning systems for overcoming the long days at home. But even if you don't get around to making a schedule for your time at home, you can still use the 365 +/- suggestions for rainy days, craft days, holidays, cooking days, etc. It's full of ideas that you may already know but appreciate being reminded of and activities you may never have thought of in a million years. And they range from simple enough to pull together at a moment's notice to slightly more complicated requiring a bit of advance planning. I love creating new projects for my kids and myself to work on, but I also love being able to pick up a book, flip a few pages and say, "Okay, we'll do this now!" Definitely worth it.
So, today's project: Clean Coins. You just put some soapy water and dirty coins out, let your kids scrub them with old toothbrushes, dry them with towels and that's it! The book suggests this will actually clean the coins, but my kids' scrubbing wasn't so effective. They take after me, I suppose, when it comes to cleaning. But the condition of the coin didn't matter a bit as my kids just enjoyed the process and the bubbles.