As a matter of fact, I suggest in this case reading a story: Earth Abides by George R Stewart. A short synopsis of the book can be found in an Extra Credit's talk.
Basically, the story explores how the knowledge that made the world before the fall run - all the high technology - has become mainly obslete by the fall as it does no longer provide a benefit for the survivors in contrast to more rural and basic survival skills and knowledge.
Society after a nuclear war will be back to about a late medieval ages, at best a renaissance, level of technology, only in some pockets in the early modern age. While the knowledge might survive in the shape of libraries or time capsules, the post-fall society will not benefit from this knowledge as it is not ready for it (anymore). However, a time capsule will not be totally in vain: preserving knowledge over this dark age in some kind of time capsule will give later generations - once they are ready for it (again) - a headstart with the new-old technology.
Contents of the time capsule
Now, what shall we put in the time capsule? First of all, it needs to be sturdy enough to survive a nuclear war and some maybe 100 years to allow society to come to terms with itself again and then another 100 to be ready to advance again. This rules out pulp-paper and microfilm for the contents but demands acid-free paper or metal engraved information in a method that can withstand the ages of time. It also has to allow deciphering the information even as the language has massively changed after these 6-8 generations. Maybe metal engraved slabs might do the trick, and writing it down in at least two, better three languages akin to the Rosetta stone might help.
One of these languages should be Math, and at least one portion of the capsule should be dedicated to mathematics, starting with the numerals and basic geometry, which allows to easily build a dictionary to transmit basic ideas.
Basic architecture (as in the design of the arch etc) should be another thing that can be easily used in the front portion of the time capsule, as it can be graphically shown and explained, making it also a good part to teach Ye olde language. Starting from there basic concepts of biology (Mendel) and physics (Kinematics) might follow, then spreading out into fields like practical chemistry (gunpowder) and engineering (how to cast steel)
I would advise against packing tools and instruments - a society develops always the tools it needs to survive. If it can't fabricate a tool it benefits from, it doesn't need it and is not ripe for it. It would be a waste of resources.