On Screen Keyboard
Warning. This is PRE ALPHA testing grade only software. It may cause your pre to melt into a puddle and dissolve while turning blue. Use at your own risk!
The Palm Pre already COMES with an on-screen keyboard. It works in portrait and landscape, in all apps, in all fields.
Press the "sym" key and a scrollable 5x5 keyboard pops up full of alternate characters.
with the layout controlled by 3 files in /usr/palm/frameworks/mojo/submissions/191.15/templates/charselector
the actual list of characters that appear on the screen is controlled by /usr/palm/frameworks/mojo/submissions/191.15/resources/en_us/alternatechars_table.json
At the simplest level then, creating an on-screen keyboard requires editing the alternate characters table json, to add the "regular" charcters to it, and then when you want a keyboard, press SYM and poof, a keyboard.
At the next level, the framework's copy of widget_charselector.js needs to be modified to not close the keyboard after each keypress.
As of 12 August 2009 Webos-internals contributor egaudet announced success at patching the framework.js to accept a new function derived from the charselector widget. This pre-alpha proof of concept on-screen keyboard is available as a patch.
The patch is on Gitorious, please read the following to install the patch: Applying Patches - WebOS Internals
The patch should be stored(on Pre) in: /opt/src/modifications/frameworks/add-onscreen-keyboard.patch
the 'source code' of the patch: 
as of 12 August 2009 the following issues are known:
- Add method to get at numbers and symbols (possibilities: sym,flick)
- Modify keyboard dimensions in landscape mode to span accross width
- Do not bring up keyboard when using hard keyboard clipboard events (might have to disable the keyboard when slider is open exposing hard keyboard)
- Enable usage to search contacts/universal search
- Fix far right column
- Verify auto-correct when space added.
- Possibly (and optionally) play sound or haptic feedback on touch
- Add clipboard capabilities
- Explore T9-type, limited-width keyboard options
- Do not bring up keyboard on swipe gestures, only tap if possible