According to MMAJunkie, UFC 109 preliminary bouts featuring Mac Danzig vs Justin Buchholz and Melvin Guillard vs Ronnys Torres will be aired for free on Spike TV before the PPV broadcast, starting at 9pm ET.
The UFC 109 card dubbed 'Relentless', has a relatively weak headliner, but it is stacked with talent from top to bottom that even the prelims would be a worthy Fight Night card in itself. I personally would've preferred to see Stann vs Davis and Gracie vs Al Turk, but it seems like they're catering to the Spike TV audience who is already familiar with the TUF 6 winner, Danzig, and the UFN 19 headliner, Melvin Guillard.
Any fight that features heavy handed guys like Buchholz or Guillard though, isn't likely to take up much of the TV time, so we'll most likely see more than those two guaranteed bouts.
The current UFC 109 card is as follows:
Randy Couture (17-10) -360 vs. Mark Coleman (16-9) +320
Nate Marquardt (29-8-2) -280 vs. Chael Sonnen (23-10-1) +275
Demian Maia (11-1) -320 vs. Dan Miller (11-2) +285
Matt Serra (9-6) -125 vs. Frank Trigg (19-7) +115
Paulo Thiago (12-1) vs. Mike Swick (14-3)
Mac Danzig (18-7-1) vs. Justin Buchholz (8-4)
Melvin Guillard (22-8-2) vs. Ronnys Torres (14-1)
Rob Emerson (17-8-1) vs. Phillipe Nover (9-2-1)
Brian Stann (8-2) vs. Phil Davis (4-0)
Tim Hague (10-2) vs. Chris Tuchscherer (17-2)
Rolles Gracie (3-0) vs. Mustapha Al-Turk (6-5)