Cripes it's been a while since I looked in mine... from memory:
Gamgee
Bandages
Ready to go poulices
Iodine
Some kind of purple powder or spray or something
Scissors, safety pins etc
Slings (for the rider)
I believe a foil blanket thing (for the rider)
Surgical tape
I have a whole box of stuff but can't remember! Oh, and a really good horsey first aid book!