An olla (pronounced "oy-ya") is an unglazed ceramic pitcher that is buried near the root zones of plants. You fill the pitcher, and the water seeps into the surrounding soil, providing your plants with steady moisture, even in the hottest, driest weather.
You can purchase ollas, but they are kind of hard to come by depending on where you live. There are a few online sources, but the shipping is not cheap. A great solution, then, is to make your own. Matt from Closer to the Dirt has great instructions (including photos) for how to make your own olla. It's inexpensive, simple, and effective---just the kind of project I like!
I'm always looking for tips like this one to feature on the blog. If you've found a good way of taking care of a common garden challenge, tell me about it and we'll see about sharing it with the rest of the About Organic Gardening community.