Palm as LCD Display
There are a few software packages out there that let you make use of your old PalmOS PDA as an external LCD display for a Linux-based machine.
You can also look at my main Palm / Treo page.
The fore-runner in this field appears to be PalmOrb, though it has been unmaintained since February 2005. Arguably, this may be due to the prevalence of cheap serial or USB LCD displays, which can be had for under $50, or slightly more for graphics-capable models.
PalmOrb essentially emulates a Matrix Orbital LK204-25 LCD, allowing you to control the Palm display using software that would be used with this LCD, such as LCDproc or LCD4Linux. You will need to set these for a 4x20 screen, serial at 19200 baud.
It emulates the Matrix Orbital 4x20 display, and adds support for colors, up to 25 keys sent to the host, and graffiti. It also supports backlight operation, and prevents the Palm from turning off automatically as long as data is being sent.
There is occasional activity on the SourceForge Forum.
You can view the install instructions here.
Here is a page containing sample code to write your own driver.
There's some information on configuring your LCD driver software here.
You can also grab this software from my server, current as of 2008-08-03:
palmorb-v1.0.tar.gz (no longer maintained) (homepage).
lcd4linux-0.10.1-RC2.tar.gz or lcd4linux-0.10.1RC2-11.1.i586.rpm (homepage) (openSuSE repo with RPMs).