I hope someone can help me to find a legitimate, honest organization to investigate unusual events at my friends’ house. They are thinking “paranormal”, I’m thinking “just haven’t found a rational explanation yet.” Either way, I’d like to have a reputable group check it out before my friend calls Ghostbusters® (or whatever scam artists are ghost hunting today).
The Chicago Skeptics sound like a good call. If you want an academic parapsychological opinion, I guess you could write to Annalisa Ventola at
http://www.parapsych.org/ and ask if there is anyone at the Chicago universities in the field. Say CJ mentioned the PA and though they might be able to refer you to an academic parapsychologist. I'd ask both along at the same time; however my gut instinct is just investigate yourselves. You can probably work out whats going on, you seem intelligent and sensible.
My serious advice is to advise the family not to discuss their experiences with neighbours, any one but close friends or especially the media. The last thing you want is a crowd of people outside the house shouting "woo ghosties" or whatever.
Some basic thoughts: everyone has already taken the right approach, in that you have to analyse each event, looking for the logical cause. Once an event causes people to start thinking spooks, then the context is set and everything else is interpreted in that way. So take each phenomena one at a time.
Nothing harmful is happening, the family sound well adjusted. It's just annoying and mysterious, but if you work on establishing a rational cause for every event the issue may disappear. Sure get the electrics checked out, but it sounds more like vibration if anything, though I don't know enough to speculate meaningfully.
Still make a joke of it, take it lightly, and don't stress or let it get dramatic. I hope it all works out for you, but record all the events (we have no idea of time scale or who was present at each event from your account) and let us know how it goes.
cj x