A site dedicated to 78 rpm discographies for a large number of companies
If you collect children's records or would like to get any information about them this site is very helpful and the book by Peter Muldavin is an excellent resource for anyone interested in this subject.
There is a great antique Phonograph Societies that I recommend to people interested in phonographs and 78rpm records. While it is more geared towards the phonographs it provides an excellent publication about the hobby. Click on the link below to learn more about it.