Bathing Suit or Tri Suit
Swim Cap--Some triathlons give you one.
Hair ties if your hair is long to tie back.
3 Towels-- One for the ground, one for your feet and one for your body.
3water bottles, or 2 water bottles and a squirt bottle with water. One is for washing the sand off your feet.
Gatorade, or Water in your water bottle on your bike.
Bike Shoes if you have them--I don't so my bike shoes are my running shoes, but something I have learned is to double knot my laces so they won't get caught in the chain.
so DON'T forget the running shoes.
Fuel--Like Gu's or Gel blocks, or Clif bars. You can have this already attached to your bike to eat while riding.
Running belt. This can have fuel in it, or a water attached.
GPS watch for your run if you like that sort of thing.
Running Shoes if you already don't have them on.
Body Glide--so you don't chafe or blister
ID to pick up packet.
Camera to take a picture of your friends and to give to your family or supporters you brought along so they can get pictures of your awesome finish!!!!
Dry clothes with underwear to change into AFTER the triathlon is done.
Money--probably won't need this, but there might be something fun to buy.
Here is a blog post I made about my very first Sprint Distance Triathlon:
This next post was one I made about my very first Super Sprint Triathlon (that is smaller than a sprint by the way). http://managingthewaist.blogspot.com/2011/07/tri-in-july-sigourney-iowa.html