Some packets will include hardiness maps, detailed instructions for how to germinate the seeds indoors, probable days until harvest and what kind of helpful insects the plant might attract. Some seed packets even provide drying instructions or recipes!
Needless to say, your seed packets are a great resource of information during all stages of gardening: planning, sowing, growing and harvesting. It can be very helpful to hang onto the packets after you are done sowing the seeds to referrence later. And if you can't use up all the seeds within a packet, most can be stored in their packets in a cool, dry place and used next season!
McLeond. Judyth Botanica’s Organic Gardening: The Healthy Way to Live. San Diego: Laurel Glen Publishing, 2002
Trail, Gayla You Grow Girl. New York: Simon & Schuster, 2005