Just because you are uncluttering your life, doesn't mean you might not want a few accessories for your Kindle. In fact, the right accessories can help you declutter even more.
Like any paper book, you can't read your Kindle in the dark (unless you are a vampire or have the eyesight of a cat and a full moon). However, you can use any reading light already present in your house. For reading in bed or when not at home, though, you may want a reading light. There are many on the market, with older non-LED lights usually having the best light, but the worst battery life and expensive bulb replacements. Many older LED lights are so dim, even with several LED's, that you can barely make out the text on a paper book or the Kindle. Also, many older designs are made to slip over a few pages of your book (not the best design) and don't work well with the Kindle's cover. The light I use and the best seller amongst other Kindle owners is the Mighty Bright XtraFlex2 Clip-On Light. This light has two brightness settings and you can read even with the lower one. The large clip grabs the cover securely, while sliding under the top edge of the Kindle itself. The only real complaint I've heard is the weight, which combined with the three batteries (I use rechargeables) can mean the Kindle is a bit top-heavy when reading in bed. However, the combination still weighs much less than a hardcover book (without a light) and is still easily controlled and read with one hand.
One of the first add-ons many Kindle owners purchase is an SD (or SDHC) memory card, for storing additional books and for any music or audio books they wish to have on their Kindles. The built-in memory may hold a couple of hundred books (less if they are in the Topaz format or have a lot of images), but it quickly fills up if you decide to copy over a few audio books or some background music to listen as your read. The Kindle officially supports only SD cards and those up to 4gb, but most users have quickly found that the SDHC cards work just as well, so long as you let the Kindle format them and create the initial directories. Just pop in a new card, then copy a book from the Kindle to the SD card. Once this process is complete, you can remove the SD card and copy to it directly from your computer or just leave it in the Kindle and use the USB cable to access it (this is probably the easiest solution). Prices on these cards varies widely (and watch for shipping on third party sellers); currently you can get a Kingston 2 GB SD Card for $7.04, the Transcend 4 GB SDHC for $8.59 or 8 GB SDHC Card for $16.29. I've tested all three of these in my Kindle and had no problems at all. I use the 8 GB SDHC Card just for audio books, as they are so large, but find the 2 gb card sufficient for holding a couple of thousand books (of course, at only a couple of dollars more, you might want the 4gb card instead - that extra space can be used for music, where the files are generally much larger than book files).
Update 1/14/09: Two of these are now available with Amazon's Frustration Free Packaging (no plastic containers to fight with): the Transcend 4 GB SDHC for $8.99 or Transcend 8 GB SDHC for $15.99. The Kingston 2 GB SD Card has dropped to $6.90. All three qualify for free super-saver shipping (I've seen the same size cards recommended for the Kindle at triple these prices, so be sure to shop around).
If you do much traveling with electronic devices or have more than one or two at home, you know what a clutter the chargers can make. And every trip means packing several chargers, as none of the devices seem to be compatible with the others. A few devices will charge via USB, but many notebook computers don't provide charging power on their USB ports (it would drain their battery too quickly if they were not plugged in), so often you must use an A/C to USB charger for those or carry the original A/C chargers (if there is one). Pack a notebook or netbook, the Kindle, your phone and ipod and your entire carry on can be full of chargers (don't check them -- your devices could all be dead or the trip completely over before any lost luggage is found). Luckily, there are at least two companies now making universal chargers that have interchangeable tips, allowing you to charge many different devices, including the Kindle, with a single charger. Gomadic has a Rapid Car / Auto Charger and a Rapid Wall / AC Charger (use the $24.95 International Wall / AC Charge if you travel outside the country and on some cruise ships) for $19.95, or the Essential Kit, which for $29.95 includes both the Car and Wall Rapid Chargers and a Kindle charging tip. You can even get Emergency Battery Charge Extender and use AA batteries to recharge your Kindle when in a remote area. Any of these is ready to go and would replace carrying the charger that came with your Kindle. All you need for any of your other devices is the appropriate Gomadic charging tip.
The second company with a universal charger is iGo. With this company, you purchase the charger and tip separately, so be sure to pick up both items (and test everything out before any trips). The iGo Everywhere Universal Wall (AC) and Auto (DC) Charger with Retractable Cable and the iGo Power Tip for Amazon Kindle will get you started; all you need to add is the appropriate iGo Power Tip for the other devices in your life and you can store all those other chargers away.
One last item some Kindle owners have sought out is a Replacement Battery. These have been out of stock for months at Amazon (Radio Shack did have some, but they went out of stock before Christmas as well). Speculation is that the battery is the main shortage behind the current two month wait for a new Kindle, as batteries have gone out of stock every time the Kindle shows a shipping delay. If so, don't expect Amazon to have more batteries anytime before March (if not later). The question is, do you really need a second battery? Unless you use the Kindle in a location where you can charge every couple of weeks, but not in between (or once a week, if you are an extremely heavy reader), a second battery may not make much sense. That Gomadic AA Battery charger may be more handy, in truly remote areas (you can buy AA batteries almost anywhere in the world and they keep their charge for months). Rechargeable batteries do lose some of their charge even when not in use, so must be recharged periodically. They also have a limited number of recharges (often in the hundreds of charges range), so you don't want to keep recharging a battery you don't use. And if you are worried about the battery not being available in later years, you can always pick one up later this year, when they come back in stock.