Moaning Disc Brakes?
Sounds like dirty pads to me, but disks can be a pain to de-squeak.

The things I'd check are...


Clean the rotors with alcohol, brake cleaner or a bottle of ethanol from the chemist.
Remove and reinsert wheels. Make sure the QRs are nice and tight, and the wheels are straight/centred properly.
Check all the bolts holding your callipers to the frame/fork are tight enough.
Rotor bolts too.
Try and bed the pads in again, 10-20 hard stops should do it.


That should do it really, if it doesn't try new pads on clean rotors. Bed them well.

You could also try lightly greasing the back of the pad where it touches the piston and sanding the pads down, cleaning the rotors, and bedding in again.