I've always made up my own..so I'll list the things in mine, forgive me if I forget something here...
Alcohol
Betadine
Hemastats (small and large; I like the curved ends best)
Blunt, dull scissors (child's type)
Unwaxed, un-flavored dental floss
Suction bulb
Lubricating jelly
Pedialyte (for mom)
Small nursing bottle (some extra nipples)
Milk replacer
Nutri cal (for mom)
Heat pad (i use the sunbeam brand, waterproof with 5 settings. about $30)
Small scale (i have 2 kinds, either would do for newborns, digital or vegetable)
Lots of wash clothes previously washed in hot water
Lots of towels, small blankets
One small syringe (no needle)
More sterile syringes with needle (i am very educated on administering oxy so I keep this on hand) let your vet do this if you are not REALLY experienced
A dropper
Rectal thermometer
Styptic powder
Disposable pads (piddle type or hospital type)
A notebook to record temps, times, weights, and your experience in general. (your vet will love you for this if any problems arise, and funny how we can forget everything at the drop of a dime when we are nervous or upset)
Now I'd like to discuss whelp boxes...
I like something that is disposable and easily replaced if I feel the need. I use plastic sweater storage boxes. You can find them in a variety of sizes. Some people like to use cardboard which is GREAT for the "actual whelp" then throw it away and move them into something else. Make sure you put the heat pad under the box and not in the box. Custom built whelp boxes are nice if they are not going to be used over and over. My husband and I looked into building these. He discussed it with our vet on exactly how it should be done. After we gathered all of our info, we decided they are just not worth it. Treated wood can harbor germs deep within the chemicals that cannot be properly washed away. On the other hand un-treated wood can also be a germ bed and hide un-forseen mold. (my husband is a master carpenter/sub contractor and believe me he knows his wood) So in my opinion wooden whelp boxes shouldnt be used over and over.
And the last thing you should keep in your whelp kit is some good, strong coffee and some eye drops because you are not going to be sleeping for awhile