I first learned about the salad table in the NY Times on May 10, 2007. They were invented by this genius named Jon Traunfeld at the U of MD Cooperative Extension.
They are basically waist-height growing tables. Easy on the back to plant and maintain (and harvest of course). Also - they're relatively light-weight (although Megan grumbles whenever I ask her to help me move one of them - grumbles reside in a few weeks when we start to harvest our lovely little lettuces and leaves!) so they can be moved according to light and temperature. I start mine in full sun. Come the first big heat wave of June every year, I move them into the shade. Come the fall, back into the sun.
I built my first one the day after I read the article about them. Click here for the instructions on how to make one.
They take about four hours for one person to make. Less time after you've made your first. You can get the materials at your local big box or mom & pop hardware store. Then buy seeds, potting soil, and some Osmocote (a slow-release fertilizer). Mix some of your organic compost into the potting soil for best results. And sprinkle the Osmocote on top for slow-release of fertilizer throughout the summer.
Two tricks I've learned to crazily improve the growth of your seedlings:
1: lay some old wooden storm windows over the tables after planting in early Spring - they'll act like mini-cold-frames: amplifying the sun and retaining heat & moisture at night
2: cut a yard-strength clear garbage bag down the sides to make a long piece of transparent plastic - lay this over them and secure the two ends with short pieces of wood - has the same effect as the glass window route
Here is a video about how easy it is to seed them...
Here is a video on their portability and making simple cold-frames for them...