If your job keeps you away from home (or you just don't want to water things twice a day), check out this simple idea from Instructables user KindleKat for a self-watering table that's perfect for salad fixings, herbs and more. It's really just a simple frame with plastic tubs. A smaller tub is turned upside down and placed inside with a piece of PVC tubing sticking out the top, dirt is added, then water and more dirt, and finally plants.
Even if you don't have time to tackle a project like this now, it's a good one to file away for later. If your space is smaller, try decreasing the size so it only holds one or two buckets making it a bit more patio friendly.