Good morning! I've scoured the web to find what--as of today--are the best accessories for the Palm Pre. Because this is my user review, I'll focus on those I chose to buy and/or would like to and why.
There is a small range of case styles available (snap on, side cases, hard or rubberized, leather, fabric pouch, with and without a belt clip) but not yet a ton to choose from in each category.
The one I use and my favorite of those that are currently available is the Palm leather slip case without any clip attachment. It's made of a very thick, sturdy leather with solid stitching, and the phone fits inside securely without being hard to get out.
The phone in the case makes for a pretty nice, understated, compact little package. It's easy to throw in a pocket or bag without worrying about the screen or phone itself getting knocked or cracked.
Adapter for Listening to Music in the Car
If you want to listen to Pandora, podcasts, or music you own while in your car and don't have an aux port (as I don't, because my car is old), the best solution is a combo FM Transmitter + USB Charger Adapter like this one.
Adapter for Listening to Music at Home
All you need to listen to your Pre via your home stereo system is a Male to Male 3.5 mm connector. At $1.02, this is a pretty simple, inexpensive, and effective home solution.
Better Headphones with Corded Mic
The Ultimate Ears MetroFi 200v Noise Isolating Earphones w/ Microphone are supposed to be a decent option if you are unhappy with the mediocre headphones that come with your Palm Pre. I haven't bought them yet, but I have them bookmarked for future reference. Amazon reviewers and people on the Pre Central forums like them as an upgrade that doesn't require you drop a lot of cash.
The most effective and cost efficient solution that I have found for just charging in the car is a simple cigarette lighter usb adapter that works with the micro to usb charging cord that comes with the Pre. If you buy it at Monoprice, the cost is .97 and well worth it.
The best home solution is the Touchstone, of course. It's pricey ($49.95 + S&H online at best), but I hear it works well (though the phone can get warm charging on it for a while) and a lot of people talk about how much they like the matte, slightly textured back cover that comes with the Touchstone. This cover is necessary because it has a magnet that allows the phone to rest securely on the touchstone base, but it also looks and feels nice (less cheap than the shiny plastic battery cover that comes on the phone).
I don't have a Touchstone (yet), but the phones I demo-ed in my Sprint store do, and I can confirm that they are much nicer than the one that comes on the phone.
NEXT UP: Palm Pre features I most like/don't like...