If you can't make it to the local nursery or farmers' market, there's an alternative. You can shop online and have them Fedex'd to your apartment or office.
We recently got an incredibly lush and healthy basil plant ($19.50) from Bloomscape and it's doing great on our fire escape here at AT headquarters. We pluck the leaves and sprinkle them on our lunch.
Bloomscape also carries oregano, rosemary, Italian parsley and tomato plants.