I carry both a wireless modem and a wired one. Since coverage isn't universal you will find yourself often relying on the ancient stick/fire method of connecting via the wired modem. Always carry both! I have found even in some "wired" cities, like New York, coverage is sporadic due to all the obstructions and bunker like buildings.
I carry two phone cords, one retractable and the other a regular 25' cord. The retractable, no bigger than a business card case, is great for carrying around in your pocket. A number of manufacturers like Targus and Brookstone make them. I use the one from Brookstone because it has a built in coupler. If you get the Targus, be sure to pick up a coupler. In a hotel where there is no data port on the phone, or the phone may not be near where you want to work, the 25' cord comes in handy. I also carry a splitter so that I can leave the phone connected to the wall to minimize having to switch back and forth.
It is also a good idea to bring a surge protector for the phone line. I recommend the one from
Curtis. This portable surge protector is fabulous. It works as both a surge protector for phone and power. Plug it into the wall and you can attach one phone line, but two separate devices (laptop and Visor). In addition you can plug-in two AC devices as well. It has three LED indicator lights for "Wiring Status", "Power", and "Surge Protected". The design is excellent and it is only about the size of a small, un-frosted cake doughnut (mmmm doughnut).
I bought the colored pack of styli that you can get from Handspring. Not only do they come in several great colors, but you'll never be without, if you ever happen to lose one. Also, in case you weren't aware, each end of the stylus unscrews. The tip reveals a pin-like bit for acupuncture or restarting your Visor. The other end reveals a small phillips screwdriver for glasses, disarming a bomb or in case you have the inkling to disassemble your Visor (resist the temptation).
I have two separate keyboards and I often carry both. When on the go, I rely on the collapsible Stowaway keyboard from Targus. Not much bigger than the Visor itself, it helps out on airplanes and meetings where typing is handy, but bulk is not wanted. It also works great as a conversation piece to break the ice (Bond, Alan Bond).
The other keyboard I carry is the GoType Pro. It doesn't collapse, but it has a nice feel to it for typing, has a comfortable slant and also serves the function of a cradle in case you need to sync with your laptop.
I suggest you invest in some type of backup device for your Visor. In case you missed it in your instructions or you are a man (so you don't read instructions), when you run low on batteries and you continue to run your Visor, you will experience a complete loss of data. This has happened to me on three occasions. After I learned what caused my first data loss, I had it happen on another occasion where a reminder popped up (again and again), turning on the Visor before I was able to replace the batteries. The last time it happened, the button on my EyeModule (digital camera) got depressed while in my pocket. Nothing smells like disaster more than an EyeModule taking live footage of the inside of your coat lining for 10 minutes. In this situation you will find that a backup device can quickly and painlessly restore all your precious data, far from its cradle.
Which brings me to...
Always carry extra batteries. Even if you have one of those rechargable battery packs. Also, many modules don't use rechargables. I have had members of the Palm Tribe mock me for not buying a Palm (which was rechargable). I was the last one laughing when their charge ran out and I was only $2 from running again. Also, if you are a heavy module user, be sure to buy brand name Alkalines. I have tried the dollar store cheapies and though they do fine with the Visor, once you add a module like the camera, in minutes they are dead, and so are you.
You know, a picture is worth 1,000 words, so the EyeModule can save you a lot of work in Graffiti. Granted the EyeModule isn't the best digital camera on the market (it is only $150), but it sure does come in handy and I use it almost every day. It's a small, unobtrusive module that is easy to use and install. I often find myself seeing something that I really want to remember. However, you can't always capture what you see effectively and quickly with Graffiti (I jus sa thc Lockncssmouster). In less than 10 seconds I can have it installed and take a picture. Once you take the image, you can attach a note to it and even beam it to another Visor. It also documents the time and date the image was taken. This feature can really come in handy, especially if you have a rental car mishap or you see Madonna sucking down a latte (cha-ching).