Sound

Go to garage sales or goodwill stores and find a cheap tape/CD player(s) and speakers. You can also look at Raido Shack or Kmart too.

If you are just having spooky music or sound effects not coordinating with any particular scene you could just have one source of music playing loudly so you can hear it throughout your haunt. But if you want sound pertaining to just one scene you can use a separate player and speakers having a tape or cd with the certain music or sounds you want for that scene.
For the tape player you can also use a loop tape. A loop take is a cassette tape that you can record something on for either 5, 10 and up to 30 seconds and that's it then it just keeps playing that same thing over and over and over, the tape never ends. So you constantly get the same sound and you never have to turn the tape over.
If using a cd player, use your computer to put music/effect sounds onto a cd. If it is for a separate scene or overall sound in your haunt, this way you can customize the cd to exactly what you want to hear. Check on the internet too. You can find some web sites with sounds or voice clips people have made themselves and are offering for your use for free.

Sometimes all you need is one very loud scream or loud horn blast to totally scare the $#*! Out of them! Try having a loud noise or scream occasionally here and there on your tape/cd or better yet just have an actual person do it!