This page is dedicated to resources for writing, querying, and publishing.
http://www.publishingcrawl.com/ – Provides information on writing, reading, and the publishing industry. They have a detailed resource page covering topics from the craft of writing to the business end of publishing. If you are struggling with writing, revising, or something else, you should check their resources out.
http://writershelpingwriters.net/writing-tools/ – Has all kinds of tools and worksheets to help you polish your writing and revisions. The page even has some marketing info.
http://queryshark.blogspot.com/ – This website is perfect for examples of what agents are looking for in queries. Not sure how to write a compelling query? Study the examples and revisions on this site.
https://querytracker.net/ – Provides tools for keeping track of your queries. The forums give you the chance to interact with other writers.
http://www.manuscriptwishlist.com/– Good site for seeing what specific agents have on their wish list. The search feature lets you search the database by agents, editors, favorites, genres, keywords, or recently updated entries, making it useful for finding new agents or editors to query.
https://www.kboards.com/– This is aimed at Kindle users, but their yellow pages listings are a good resource for writers looking to hire anyone from editing to marketing help. The forums provide an opportunity to connect with other self-published authors.
https://authorstash.com/– Provides listings of tools and resources, including professionals for hire. So far this site doesn’t have as many listings as the yellow pages on the kboards, but it appears to be slowly growing.