LogoLanguage for PalmOs.
Limited logo but small (total impact about 80kb) and fun to play with if you are learning basic logo. The simple graphics stuff works and there's a good set of examples.
Well thought-out standard for storing the logo procedures in memos and simple Palm integration for reading and writing memos makes it useful for quick hacks to process text on Palm.
Lacks a lot of the more advanced constructs in BrianHarvey's UCBLogo so can get frustrating very quickly if you are trying to become a savvy Logo programmer. I found Logo itself a fun way to learn list-oriented, recursive thinking but as a longtime OO person have devoted my energies to learning PythonLanguage as my latest language.
Requires the PocketC runtime interpreter. Being based on this means there's an awkward means of entering text requiring use of the scroll up key.