Below are the three songs included in my old Roland JV-35. While the standard GM complement of samples sounds a bit dated, I always thought these songs were well done and did a good job of showing off the keyboard. Unfortunately the expansion board didn't include more ROMs... the wide range of sounds on the board are really good.
On the whole the old keyboard has served me quite well, though the MIDI-in port is malfunctioning at this point. At some point, I'll grab a keyboard with weighted keys (and a full complement of 88), but for now I'll the the most out of it I can.