If it's originally good hay and not completely molded (which is what this sounds like) then you may be able to sell it to some cattle men; they'll probably want a bargain on it though.
If you can't get pallets into the hay storage room, then trying laying out a grid of four by four by tens or twelves to get your hay up off the ground and get some circulation underneath it. Another thing you can do to help prevent this from happening again is to salt your hay really well when you stack it (sometimes hay can be a bit wet in the middle and this helps, plus the horses and other livestock appreciate the salt).
I've had some hay get moldy on an edge with the rest of the bale still being good, and you can try pulling apart the flakes to get rid of the moldy part (this was prime $7 a bale alfalfa that had unfortunately gotten stacked in the wrong spot -- I definitely wanted to try salvaging some of it). It was messy and wasteful, but the horses were fine on it and not a complete disaster like throwing the entire bale out. I've had to settle with hay that had some dust to it too during lean years (two years ago hay could not be had for love or money around here due to a bad season), I got by feeding as little as possible and watering it down before I fed (they wasted a fair share but not as bad as having no hay at all) and I had to supplement with hay cubes and beet pulp quite a bit until my hay guy caught a break and got a decent stand to bale. In neither situation was the hay in truly unsalvageable condition -- and I had my horse vet take a look at it and tell me what he thought.
*Oh, and stack the bales on the narrow, long side -- less area space per bale touching a potential mold producing spot.
