Well, with a lot of help from the nice listers at Macscripter.net, I came up with the following AppleScript. Save it into ~/Library/Scripts (I use the name makeMemo.applescript), make sure the AppleScript menu is visible in your menubar, and off you go. When you want to make a memo in Palm Desktop while surfing in Safari, just select the text and choose the makeMemo script from your menubar. A new memo item will be created. Tweak as desired.
tell application "Safari" to set contentsTxt to ¬
(do JavaScript "getSelection()" in document 1)
set contentsTxt to «class ktxt» of (result as record)
set titleTxt to text 1 thru 20 of contentsTxt
tell application "Palm Desktop"
activate
try
make new memo with properties ¬
{title:titleTxt, contents:contentsTxt}
on error msg
display dialog msg
end try
end tell
[robg adds: I haven't tested this one...]

