What's your best recommendation for a PDA that's compatible (fully so) with Linux?

I'm looking for one that lets me work on Office 2007/openOffice doents, spreadsheets, presentations, etc, as well as has wi-fi, good support for expansion cards (or high internal memory) as well as various multimedia formats. I don't care if it's windows mobile or something else, but I'd like to have a full featured imap client on it and be able to work well with linux when syncing files, doents, etc.Thanks!