GlobalWare has a product called Pylon Conduit which does C&S and email sync w/ the PalmPilot. They also have a product called Pylon Pro that can even convert some Notes applications to run on the PalmPilot.
Puma Technology has IntelliSync.
Lotus has EasySync but the other products have more features.
Cadenza from CommonTime can synchronize mail, calendar, and contact info between Notes and a PalmOS device.