Make sure to find out your frost free date so that you can time it correctly. For example, I wont start my tomatoes for at least 4 more weeks. However, I have already started onions, lettuce, swiss chard, broccoli, cauliflower and brussels sprouts. You can also do cabbage, celery, eggplant, spinach and others. When it comes to the right time, I will start tomatoes and peppers. I just did a post on correct timing and such on my blog and even posted an excel spreadsheet that if you enter your frost free date it will give you all the correct planting times. The link is below. Good luck.

Here is a link that might be useful: VegeNag Blog