As part of my research sources, I have an extensive library on a variety of topics.
The page has a dropdown menu from which you may select a topic of your interest and find related dictionaries or books:
This is the opening page of my library.
Note 1: you will not find school-level dictionaries here. These are highly specialized, expensive volumes.
Note 2: The above image illustrates Delicious Library 3.0 for Mac.