download a program called "handy book" from epocware
direct download. it's actually an ebook reader for symbian.
but in the package, there is handy book converter; it takes txt files and converts them to .pdb. it also has a nice feature where it automatically recognizes a number at the beginning of a paragraph, thus making an index of all the available chapters.
the converter inside the demo download works fine on windows xp, so far i haven't seen an expiry date.
on the peanut express site there is a program called palm ebook studio, which is a wysiwig editor for ebooks. it actually shows you on your screen, what the result will be on your pda. costs $29, and is available for windows and macintosh.