Good for you for thinking about having a first aid kit on hand!
This is what I recommend:
Triple antibiotic ointment
Hydrogen Peroxide
Hydrocortisone cream
Alcohol swabs
Benadryl
Pepto Bismal
Kaopectate
Baby Aspirin
Self-adhering bandages
Gauze pads
Eye wash
Small syringe (no needle) marked w/m’s or cc’s for medication administration
Cold Pack
Styptic powder to stop bleeding
Cotton swabs/cotton balls
Thermometer (normal rectal temperature is between 101.0 to 102.5 degrees)
Copy of shot record (in plastic sheet)
Pedialite to replace fluids
Also, I'd download a copy of the Red Cross's first aid for pets and keep it in a plastic sleeve in your first aid kit:
http://www.redcross.org/services/dis.../firstaid.html