I've often wondered if it would be feasible to have a searchable online database of worked out "first nontrivial examples". Users could upload their examples to the database and these could be community-refereed much like answers from this site or MathOverflow.
Certainly many textbooks contain such examples for undergrad material, but for research-level stuff this becomes more difficult to come by. It would be an efficient thing to crowdsource.
This question is a poor substitute for the above, but:
What are some hyperlinks to fully-worked "simplest nontrivial examples"?
In your answer, please indicate what your link will provide a basic nontrivial example of. If the example appears in a paper, please provide the page number and label for the example that is given in the paper.