How can I pour a concrete floor over a particle board subfloor?
Frankly, Stacey, the thought of a concrete-over-wood floor frightens me badly. IF you can determine that your existing framing can carry that much additional "dead load", then definitely rebar and remesh (the mesh) well or it'll crack. You should know that the floor will want at LEAST 2" of thickness, which means each square foot of flooring will weigh at least 25 pounds, so the floor for a 12'x12' room would weigh a total of 3600 pounds (nearly two tons).

Talk with your local concrete companies - they may be able to mix a batch of lightweight concrete for your purposes - if you're dead-set on this. It WOULDN'T hurt to employ an engineer to verify that your structure will tolerate that much extra loading, though.

You do know that the concrete floor will be very cold underfoot, right?

EDIT: ...and that it'll always generate "concrete dust"?