We were going through a box and I discovered some items that I had forgotten I had and I need to know if they're worth anything...I'm afraid to ask so here we go. If this isn't the right spot to ask this, please point me in the right direction:

Doug Henning World of Magic (like new)(picture on front cover of him sitting down with legs crossed in the clouds) Souvenir program

LeGrand David Lecture Notes from the late 80's

Siegfried and Roy Beyond Belief "An amazing spectacle" from Frontier Hotel&Casino Souvenir program

And picture holder for autographed picture from Frontier Hotel with Siegfried and Roy on cover...

Thanks for your help

You have some cool item's there.
As with most collectable's they are worth what someone else is willing to pay.
Many coins and stamps have a book value just as many sports cards do but they too can only fetch what someone else is willing to pay (many times below book).
A Doug Henning fan most likely will pay more for your souvenir program than a person just interested in Magic in general.
I collect beer cans & bottles and have often payed more than the true value of an item just because I wanted it very badly and I could not aquire it at the fair market price.
Iven