Have you seen the commercial for the water globes? They are these vase looking glass bottles that you fill with water and put into the soil in planters that water your plants as needed. I'm not sure of the specifics but the water actually does drain into the soil over time and not all at once.
I use wine bottles. They're free (kinda). They are for me because I don't drink wine and I ask friends to save me a few bottles here and there. Okay, so I will have a spritzer now and again but I'm a beer girl, really.
I think they look nice too.