I had a lot of suggestions from gardeners about their seedling shelves. The best deal seems to be the assemble it yourself. This is a 35" wide x 54" tall x 18" deep metal shelf system with 4 shelves ($67.54). I have 1 shop light fixture ($8.97) hanging with adjustable chains on each of three shelves to start. Each fixture holds with two 40W 48" fluorescent bulbs. I can expand and use the forth shelf later if I need more space. Each shelf holds two planting trays, lengthwise. They hang over the edges a bit. I bought a mix of Grow Light bulbs ($9.99) and full spectrum bulbs ($6.47). Together with a plastic floor mat, it cost about $165 and is very sturdy.
Here's a commercial set up for comparison. The Delux version has 8 bulbs for 8 trays ($439.95 not including shipping). Mine has 6 bulbs for 6 trays now and room to go to 8 bulbs and 8 trays.
I looked up some information on lighting:
From Gardeners.com: "Cool white bulbs are a good source of blue and yellow-green light, but are a poor source of red light.... Plants grown under cool white bulbs will be stocky or even slightly stunted. Warm white bulbs emit plenty of orange and red light, but less light in the blue and green spectrum. If you are growing seedlings under 2-bulb fluorescent fixtures, you can usually achieve a good color balance by combining one cool white and one warm white bulb....Full-spectrum fluorescent bulbs produce a balance of cool and warm light that replicates the natural solar spectrum. These lights are excellent for seedlings."I figure I have 80 Watts per 3 square foot shelf - about 25 watts per square foot, if I keep the lights low to the plants.
Also, from here: "Seedlings thrive with 15-20 fluorescent light watts per square foot."