The new list; this is what I plan to take (stuff I still don't have in red):
* Bug Repellent
* Repair stuff
Extra Tubes (3)
Patch Kit
Tire Pump
CO2 cartridges and dispenser
Tire Wrenches
Multi-use Bike Tool
Chain Lube
Duct tape
Latex gloves
Paper towels (cut a partial roll in half, pull out the cardboard center, compress)
* Bike gear
Bell
Headlights and rear blinky
Bike Lock
Helmet
Shower Cap <-- I would not have thought of this; thank you, Zen!
Thick Rubber Bands (for brakes when off the bike)
*First Aid Kit
Band-aids in various sizes
Bactine wipes
Regular handwipes
Neosporin
Gauze pads
Pain meds (aspirin and ibuprofen)
Benadryl
Latex gloves (so I don't need to go through my saddle bag to get the other pair)
Tweezers
Chamois butter
Cortisone cream (this almost rates as a toiletry, given my heat rash issues!)
Mylar blanket
* Two Water Bottles
* Pocket Knife
* Matches
* Clothes and toiletries
Bike Shorts (3 pair)
Socks (4 pair)
Tee-shirts (4)
Shoes (1 pair)
Bras (2)
Underwear (4)
Khakis (1 pair)
Toothbrush and toothpaste
Deodorant <--- probably the most important thing on the list

Face stuff (Oil of Olay)
Small bottle of shampoo, small bottle of conditioner
Hairbrush
* Food
Power Bars (7 large, 7 small)
Trail mix (2 kinds, one with chocolate, one without)
Powder for water flavoring, in case I need it
* ID, Credit, Cash, Medical Insurance Card
* Wet Towelettes
* Trash Bags
* Cell Phone and Cell Charger
* iPod Touch, Charger, and Earbuds
* Camera
* Small Journal and Pen
* Notebook with maps, info, hotel reservation confirmations
* Book on C&O Canal
I looked at the camping gear and found one poncho, but it's a kid's size. I have a windbreaker that I lent to my kid; if I find that, I'll take that, too. divingbiker, I appreciate your offer of a loaner, but suspect you are of more reasonable size than I am!
I was in REI for a while yesterday; they are having a sale. I looked at jackets there, but they do not have anything in my size, which was okay, because they also didn't have anything in my price range!
Thank you all for the advice and good wishes! I really appreciate it. Preparing for this ride has helped make a difficult summer much, much better; thank you.
An aside... Years ago when personal computers first came on the market and I was getting one as an early graduation present, my mother remarked that they were like Barbie dolls: it's not enough to have just Barbie. You need the outfits, the Malibu beach house, Ken, clothes for Ken, the convertible...
So it is with bikes. You get the bike, and then need the floor pump, the minipump, the bell, the saddle bag and repair stuff, the rear rack and panniers, the cyclocomputer, the back blinky, the biking shorts and gloves and shirts... and so on. I've spent more on stuff for my bike this summer than I spent on my bike, and that's even if I leave out the recent maintenance bill!