American Society for Indexing
The American Society for Indexing, based in the USA has a well-organised website with useful information for editors and authors.
The Society is affiliated with ICRIS - the International Committee of Representatives of Indexing Societies, of which there are many.
ICRIS in turn is affiliated with The Indexer, the International Journal of Indexing.
This journal is devoted to archane but practically significant details, and one its authors has won an Ig Nobel Literature Prize for a study of the word "the". I encourage Research Cooperative members to see the "the" article!