This is just a page of additional resources. Personally I find it so tiring to look through everything, and then to have to deal with the added frustration of outdated information and dead links, I generally give in to despair.
Poets and Writers Agents Listings
Writers Market (requires monthly subscription). This is the web site of what used to be the major source of resources prior to the internet. They still publish their series of books: Writers Market, Novel and Short Story Market, Agents Market, Songwriters Market, etc. Purchasing any one of these books used to, and may still give you access to their online search tools.