I have a minor hay problem too. I bought a sq bale for SL and didn't use it. It got wet, so it's not food anymore. Any other practical use? I just hate throwing things away.
If it's still got the strings on it, use it for a fall display, with pumpkins and indian corn and stuff like that on it and set a mum or two around it. Some people like to stuff a scarecrow and set them down on top of it. Hay's too scarce around here to be doing that kinda stuff this year though. Anybody who touches my hay for a display this year is gonna DIE. ;o)
If it doesn't have seed heads on it, it's good for mulch if you ever get cold and need mulch. It makes good bedding for the dog if he's not allergic to it.