Which palm should I buy?

Well, as far as Japanese learning goes, what do you want apart from a Flashcard system and a dictionary? There's major players for both Palm Pilots and Windows CE machines, and I'm soo devided that I have both. For the Palm, as mentioned by norgus there's Dokusya and PADict, those programs are both VERY good, I used only Dokusya in first year, but I don't seem to use it much anymore, PADict is fantastic, the kanji-input recognition has saved me hours and hours of work (some say this is bad, but...) but I guess if you had a Japanese OS or an IME on a Windows CE machine it would be just the same, I will look into that. As for Windows CE machines there's the JWPce / JFC suite, which is completely free and totally rules. These programs are why I needed a CE machine aswell, JFC is the best flashcard system I have ever seen, the control you have over the cards is exactly what I need for school, I usually make vocab, single kanji, compounds, grammar cards and even just notes, example sentences, anything I want really. I try and 'learn' whatever it is while I'm making the cards (kinda like the first test run through a set)　and then I'm all setup for review. Also if you're doing RTK there's KanjiGym for Palm Pilots. That's basically my setup, but I have played with other software aswell, so I will try and help you make a good decision if I can. I'd probably suggest getting a Palm Pilot at this stage, but...