Okay...well, I have had two homebirths with two completely different midwives. The first was very grounded, very solid, very stress absorbing. The second was, well, a little ADD, and 7 months pregnant when I gave birth. Their lists were different and similar in many ways.
When it comes to the birth, you want to give yourself as many options as possible. You may have had a water birth last time, be planning for a water birth this time, and it may just not happen for one reason or another.
So...I suggest, having the tub stuff ready, tarps for underneath, towels for you, and whatever. Also plan on having some towels for the birth.
A couple of towels and a chucks pad will catch a baby just fine if say, you are in the bathroom.
Also get the bed ready. A full set of sheets, a shower curtain (dollar store is perfectly fine, just make sure you air it out several days before you need it to off gas it), then another set of sheets. The idea being: give birth, remove sheets while you are going to the bathroom and then you have a place to come to right away.
Also consider a flannel tablecloth in case you birth on the edge of the bed or something.
Keep everything together and ready but packed in sections so you can access it easily. Pack all your medical supplies in plastic bags. Pack the stuff for the midwives in one basket. The stuff you will need right away. And the stuff you will need the following days (including at least one change of clothes for everyone in the family)
I'm not sure what your plan is for your other child(ren) but if they are young, and you want there, teach them something to do. I taught my then 2 yr old son to sit on my tailbone (very nice), roll a rolling pin on my back, and hold a glass of water and put the straw in my mouth. So if you are doing that, you will need those things as well.
Oh yea and get a ton of hydrogen peroxide for the laundry afterwards.Kawa Kamuri has a comprehensive list and I'm trying to think of what else might be useful. I think stuff like tennis balls, rolling pins, folding chair to help with labour pain might be nice.
I also would consider putting like three meals in the freezer. But most people have friends and family for the birth and after (I had neither). I would also consider a gas lamp and matches (this made all the difference for me), some music (I had a gieco commerical stuck in my head for 27 hours for my first birth "take a train to happy town, whoo whoo" and I had a song from my son's tv show the second "I have a friend...a super swell friend" for about 8 hours) Some aromatherapy (incense can backfire very quickly) and a protein shake or some electrolyte drink ready to go as well as this is hard work and you may need to refuel quickly.
I wouldn't buy more towels unless you have few towels in your house.
Being prepared and organized beforehand will allow you to be calm and relaxed and focused on that which is truly important. If you have trouble just make a list and cross something off each day.