The think different campaign marked the return of steve jobs in the 90's. as stated before they measured 24x36. They sold them at various macworlds but they were prominently sold at the apple store on apple's main campus in california.
The smaller one's 11x17 were part of an educater's set that were given out to teachers.
The rarity of each 24x36 poster is different.
I've read that there is an ultra rare version of the Picasso one, a picture they used without permission with his hand covering most of his face. It was immediately changed to a licensed photo.
Other really rare ones are the Buzz Aldrin.
The most rare are the "Director's Series" ones that never came out to the public but there are some prints of them that were circulated. Although Hitchcock is a director and some might say THEE director, he was featured in the first series that came out that was avalaible to the public (not the director's series).
I would agree there isn't a very comprehensive guide to these but if you cross reference the things people do say about them, you'll be able to deduce the truths from fiction. Ebay has a buyer's guid but it only truthfully references the 11x17 educator's set.
on a note about your posters. They should measure 24x36 (which it looks like they do), unless everything else in that picture is for some reason bigger then they should be (perspective aside). I'm not sure if laminating them (though well preserved) was a good move as it probably decreases their collectable value.
any 60x48 poster was made for public ads and are also rare, however the ones you show are not those.
another note, texas mac man shows the picture of the poster but that's not the cropping they used on it. If you look at the TM for the hitchcock fund I believe it is a thumbnail created by them at one point. All of the hitchcock posters are cropped right at the edge of the brick to his back, like your's also show. The image is slightly misleading if someone was looking for a picture of the poster.