VOTE: fldigi I've been using fldigi for many years, it is quite simply the best and most useful cross platform data mode software in existance. It's regularly updated and the author is responsive to help requests and queries.
VOTE: fldigi One of the best (if not the best) datacomms programs out there. Multiplatform, multimode. It's the ideal software for casual data QSOs for full blown contesting.