I'm the founder of the GNU Radio project, http://www.gnu.org/software/gnuradio.
We're building a free software toolkit for constructing and deploying software radios. Among other things, we've currently got an HDTV transmitter and receiver working.
The receiver takes in IF samples at 20M samples/sec and converts them to an MPEG transport stream. The resulting transport stream is playable using xine (http://xinehq.de) or other players.
We've got a fledging wiki going also. Please visit http://comsec.com/wiki if you get a chance.
-- EricBlossom