A dozen clockwork mice. Wind 'em up and wedge 'em in so they won’t go until the wall is removed.
May as well scare the shit out of the future generations.
Also, a rubber chicken.
And a whoopee cushion.
Don’t bother with a wine. It will be ruined by the temperatures in the attic.
I think something from a semi recent computer would be neat, especially if it has the papers describing how it’s the latest and greatest.
Receipts for common purchases would give the openers an insight into what it cost to live in our times.
Woo Hoo! My thread was linked to! Go me!
Maybe you could throw in some magazines, from “Time” to “Entertainment,” so the astromen of the future can marvel at our accomplishments!
Oh, and a Mr. Potato head. I don’t know why, but it just seems appropriate. And a quart of milk.
A slinky and a Magic 8 Ball.
I work in a museum.
Not too long ago, we were extremely excited about a new find. A statue of a famous man in our town was moved, and a time capsule was found. I was literally jumping up and down as it was cut open, waiting to see the treasures within.
I think we were all pretty disappointed. There were coins, newspapers, and a few pamphlets advertising popular causes of the day. The only exciting item was a note which one of the bystanders had inserted; a brief auto-biography, and his hopes for the future. (He hoped all reading it were Christians.)
What I wouldn’t have given if that box had been filled with notes like that. Diaries, personal greetings and things like that are worth a thousand newspapers to historians.
I once found something along these lines in an old house. We were stripping wallpaper, preparing to paint, and suddenly, I discovered some sketches on the wall. The original owner, before putting up the paper, had drawn caricatures of his wife, his sisters (who apparently lived there) and his kids. Underneath each, in a lovely looping, hand he had written a little poem, teasing them about their faults. We decided to paper over them again, rather than paint and destroy them. Maybe in another hundred years, they’ll be discovered again, along with my sketches, which I added to another part of the wall, and the little note I left.
Put something personal inside. Write a letter to the future. Write a brief biography, and tell them what you were doing in the house. Add a picture of yourself. Make wacky predictions about the future. Print out a thread from the SDMB on a current topic and put it inside. (Written opinions of the common man are gold.) Whoever finds it will appreciate it more than a newspaper.
Whatever you do decide to put in there, make sure you seal it up well. I suggest sealing everything in a plastic bag. Don’t use any staples, or scotch tape.
I think you should print THIS thread out and put that in there. 
Not only this thread but you should buy the Straight dope servers and put them in the capsule.
And only because I smoke and its been done, But a good pack of lucky strike. Yes they still make them and well they would be worth something Like the WWII packs are today.
These people were quite disappointed, too.
State quarters, and a model of the World Trade Center.