You might want to check out the Growing From Seed and the Growing Under Lights forums as well as the Vegetable Forum, if you haven't already.

Lettuce does great direct sown in the garden in early April, depending on weather. It can be started inside if you want to get a couple weeks jump on the season but it's not necessary. Broccoli is usually started inside a few weeks earlier than when you plan to transplant outside (sometime in April). Tomatoes are usually started inside 6-8 weeks, and peppers about 8 weeks, before you plan to plant out (which would be late May or even early June for these since they need warmer weather and soil).

Rodney

I agree with Rodney's calendar for planting. Timing of spring planting is tough, as weather is so variable from year to year. Do keep a notebook, that will help you figure out average date for outdoor transplanting for your particular location, and move backwards from there for starting seeds. Since lettuce germinates so readily and has a quick turn-around, few people begin this indoors. Depending how long your seedlings are kept indoors, they may need a bit of fertilizer to sustain them. If you prefer organically applied nutrients, you should be able to find organic fertilizer products even at a box store. For seedlings, at least halve the recommended fertilizer rate on the product, as seedlings need dilute fertilizer only. You do not want to over-fertilize plants indoors, where the light is of relatively poor quality compared to outdoors. They should not need fertilizer for the first 3 or 4 weeks, but this depends on how often you water and your water quality. There is a learning curve on first time gardening, so think of it as part experiment. Good for you.