I have a Jornada 820 and I like it, and I think it'd be a great linux device. At this time, the only PDA in the same league is the new Zaurus SL-C700 (that comes with Linux installed - yummy). The Jornada 820 is not as fast, ramful and colorful as the SL-C700, but for most uses, you won't see the difference, and the 820 has a bigger keyboard and quite a few perks, too.
However, I realize I don't have the time and dedication to complete a useful port of Linux to the Jornada 820, and the WinCE port of Emacs is not so stable. So I'm raising funds to offer a machine and a bounty to a hacker who would volunteer to complete the linux device driver support for this device.
So if you own a Jornada 820, or intend to purchase one, you can send funds to the e-gold.com account 104835, and I'll use them for the purpose of completing the Linux port.
If you're a kernel hacker, and would like to own a swell PDA for which you can tell "I completed the Linux kernel port to it", then contact me! Details follow.
The HP Jornada 820 is a great little PDA. It's light and small: 246 x 178 x 33 mm, 1115g. It has a real 8.2" VGA display (640x480 8bpp, backlit), an almost full-size 74-key keyboard. The CPU is a 190MHz StrongARM-1100. It has 16 MB of RAM (and 16MB ROM for WinCE 2.11 -- there also exists a rare 16 MB RAM expansion kit). It has one PC-Card slot (for e.g. an ethernet NIC) and one CompactFlash slot (for your linux kernel and distribution), a USB host port (you can plug a mouse or anything), power management (batteries may last up to 10 hours of activity and more!), sound mono output and input, serial port and IrDA, VGA port (up to 1024x768 8bpp), and US version even have a software modem (I don't expect any Linux driver to support that, though).
If only Linux or BSD would actually run on it, it'd be a truly great machine, a dream machine even. Currently, the Linux kernel boots, but only the serial device is supported. Framebuffer support is almost ready, but requires some configuration with known values. Documentation is available for all the chips involved, but the wiring is unknown so some guesswork is needed still. We're trying to locate some of the engineers at HP who designed the thing, but it's not certain that we'll be able to get any useful information. I keep everything about the machine on my home machine's FTP server samaris.tunes.org, user jornada, password 820.
Note how I listed the devices in decreasing order of importance to the users who fund the project: a partially complete kernel (say, up to power management) is worth the hacker keeping the machine and getting part of the bounty. With a complete kernel (up to VGA port), he'll get the full bounty. A BSD hacker is welcome, but only if he commits to complete the kernel support up to the VGA port -- I won't settle with partial completion on a kernel for which it's difficult to find another hacker.
If you want to participate on either side of this bounty-based development, or know someone who could participate, please contact me.