Your rabbit in carriers. The carries should be leak proof.
Any paperwork you need for the rabbits from pedigrees to entry forms. If you will be registering any rabbits, make sure you have all the proper paperwork with you for it.
Litter for the carriers, bring enough for the trip to the show, the show and the time home.
Food and water cups (or bottles), you will need 1 or each for each carrier/rabbit.
Enough food for the trip as well as water. Some places don't have lots of water avaliable, so check the situation before you go. If you give hay, make sure you have enough as well. Any suppliments you give should also be taken.
Grooming supplies. Nail clippers as well as brushes. Some breeds may need other stuff.
It can be a good idea to bring some of your rabbitry info. This can be business cards or a sign with your info.
If you are taking sale rabbits, have pedigrees and other info with you.
A chair is a good idea as not all places can provide them.
Bring some blankets or something to cover up your carriers overnight. Some places can get cold at night. Lock for the cages are also good as you never know what could happen overnight.
For you, bring food and drinks for the day. While there might be a concession, don't count on it and you might not have time to go out for food. Wear suitable clothing. Some places are cold and some are warmer. Take cash, you may find a rabbit you like or want something in the silent auction/raffle. You will also need whatever you need for overnight in the hotel. Wear comfy footwear.