My south windows (well, all windows in this house) have very narrow ledges, so it's difficult to use them for anything. Earlier this year, I decided to sprout some sunflowers and found that I could use very small square containers set on a styrofoam meat tray, balanced on the narrow ledge. The pots get sunlight all day long and the sprouts grew well.
Silly me. I finally decided to use that method to start some seedlings for the garden. i am experimenting now and if it works, I will save a little on the electricity it takes to run a second grow light.
Yesterday, I planted 8 radishes, a pinch of marigold seed and a few onion seeds that might be too old to sprout. I am saving the good seed for a little later.