I was looking for a list of the tables and fields in SAP B1 and found a great page:

https://help.sap.com/doc/089315d8d0f8475a9fc84fb919b501a3/10.0/en-US/SDKHelp/Table_Overview.htm

This site maintains a similar page for the JD Edwards application:

https://erpref.com/

So while I was at it I thought I would see if anyone had done something similar for Great Plains. I found a few sites.

http://dyndeveloper.com/DynModule.aspx (some info members only)
https://victoriayudin.com/gp-tables/
http://gptables.azurecurve.co.uk/

This type of information is usually available directly from the vendor, but often those resources are restricted to licensed users with a support account. The sites above are open to the public. If you know of has a similar site for another application, let me know and I will add it here.