I figure since Google Sets used to exist and somewhat still does, there must exist some API (google or otherwise) where I could send a category as a GET request and retrieve a JSON listing of items in that category.
For example:
In: 'sports'
Out: {'basketball', 'football', 'baseball', 'hockey', 'soccer', 'lacrosse', ...}
In: 'animals'
Out: {'dog', 'cat', 'fish', 'bird', 'horse', ...}
I'm thinking that the answer might have something to do with Google's custom search API, or perhaps even Wikipedia?
Thanks!
Your best bet is probably an MQL query to freebase
http://wiki.freebase.com/wiki/MQL
Something like this for sports