Packing for Pennsic can be an interesting endeavor if you've never been. Here are some basic guidelines:
Tent - canvas will stand up to most any weather. If you have a modern tent, bring an extra tarp, ropes and stakes to put over your modern tent. It might be fine, but you'd hate to discover a leak in the middle of the night.
Bed and bedding - try to sleep on something off the ground to stay dry. However, if you use an air mattress, remember that you'll need as much insulation under you as on top. Pack enough bedding that you can be comfy in weather from about 40 F to 80 F.
Clothing - Pack a wide variation. Pennsic can be hotter than heck, with days over 100F. It can also be rainy for days on end. (Not usual, but there are usually at least one or two rainy days.) At night, it can drop to 40 F. I can highly recommend wool and linen as your fabrics of choice, though a few cotton outfits for daytime and low expense will serve you well too. You can go off site to find a laundry. (Don't plan on using the machines at Pennsic as there are only a few for 12,000 people.) Make sure you pack either a cloak or a large swatch of wool to stay warm at in your nightly travels. Here is a more indepth list of what clothes to pack.
Food - if you're going to buy it all from vendors, you'll only need a mug. If you're going to cook it yourself, pack everything from pots and pans to knives and forks. The Baronial camp has hot running water and a double sink to do dishes in. You probably won't need formal feast gear and many people do use disposable plates and silverware. If you are going to cut meat, bring antibacterial soap or bleach to disinfect surfaces. Bring a cooler if you want cold drinks or cold food. Ice is available on site. I believe last year it was $1.50 per bag. If you use an old water jug with the top cut out to put your ice in, you won't have ice melt water which gets very icky quickly. If you bring a blanket to put over your cooler, it also helps insulate it from the heat of the day and makes your ice last longer.
Toiletries - WEAR SUNSCREEN - most of us aren't used to being outside quite so much. I often get a large bottle of unbranded and put it on the table in the common area. Bring any meds and prescriptions you'll need. Include a small personal first aide kit.
Money - unless you're absolutely not buying anything. (Yeah, I want to see that, especially with the ice cream place on a hot day or when you see some fabric that would be just perfect for...) However, budget yourself.
That is the basics, for most of us there is much more: armor, pet projects, my four poster bed and closet...everyone has a list of "can't go a week without" list. Think about it in advance and go through a couple of days in your head and write down everything that you'd use. Then have an old timer check it.
Baroness Moira MacGillavrey
Baronial Land Agent for Pennsic