Were you to plant a time capsule to be opened at the next millenium..

My picks:

Complete manuals for deciphering the various media formats common to the 20th century.

Several dozen samples of completely unaltered human DNA, so that geneticists of the future will know exactly what “natural” humans were like.

Full documentation of the origin of Scientology, so that a thousand years from now when Scientology has become the dominant religion of the human race, dissidents will be able to debunk the myths that will have arisen.

Are you saying you don’t accept L. Ron Hubbard as your Lord and Savior?! He died for your sins, you know!!

(Note: Sarcasm in the above posting may not be so labelled.)