Bring Advil. If you tend to get sore, start the day with Advil... it works wonders.
I recomend the Airhawk Seat Pads if you do long distances (700-1000 miles per day).
http://www.rlmotorcycles.com/cgi-bin/eShop/index.cgi?cart_id=1247362781.41966Large barbage bags to cover the T-Bags. Mine tends to leak at 70 miles an hour and several hours of rain. Need really good rain gear too.
A GPS is great for long trips. Each morning you plot your trip. You don't have to worry about getting lost. Also great to plot the "last" gas station and make less stops. Find out of the way places or stop at each harley shop along the way.
Peppermint lotion for the feet, especially on hot-hot days. Start the day by putting lotion on your feet. Hey....my freind who used to play for the NFL and beat people for a living does it!
AAA card with motorcycle endorsement. The Harley Owers Group towing thing never worked for me. Every time I called I had to wait hours and I'd call AAA and they would show up before Harley.
If the wife is a whiny....leave her home!