JPilot - works well. Dig up your old palm pilot, visor, or clie, and put it to work. I'll submit an extension unless someone beats me to it.
You'll need source:
most recent jpilot (jpilot.org)
most recent pilot-link (pilot-link.org)
libusb.c changes (get the pilot-link-base.tcz extension, unsquash, find -name libusb.c)
Both compile readily. For pilot-link, see the build script in the custom scripts forum. Jpilot needs the pilot-link devs.
JPilot won't run without pilot-link + deps, and glibc_gconv.