Here are some supplies I have gathered in preparation for the birth. To be completely honest, I don't really "need" most of them. I think the most important birth supply is lots & lots of towels.
Chux pads (rectangular absorbent pads, aka incontinence pads or puppy training pads)
Placenta Out tincture (for bleeding before placenta releases)
HemHalt & Wombstringe tinctures (for post-placenta bleeding)
Afterease Tincture (for relieving afterbirth pains)
Herbal afterbirth bath: great for healing tears & sore bottoms
Placenta bowl (aka a large, shallow stainless steel mixing bowl)
Emergen-C (a powder you add to water, to make a fizzy, energizing drink)
Various massage tools
Microwaveable rice packs
Electric heating pad (for keeping towels warm)
Things I have but will probably never use:
Plastic cord clamps (I plan on tying off the cord with shoelaces or braided embroidery floss--much more comfortable for the baby)
Nonsterile latex gloves (mostly for when I am at someone else's birth and examining the placenta)
Sterile 4x4 gauze pads
I plan to put all of my birth supplies in a basket that I can grab and bring anywhere in the house. I will layer the supplies with things I will need first towards the top, and afterbirth/baby items towards the bottom.