Check out Marci Seidel’s blog. She has a great annotated list of other blogs by authors, agents, and book industry people giving great advice about query letters.
Ask the Agent
Night Thoughts of a Literary Agent
The Literary Agent’s Guide to Writing a Non-Fiction Book Proposal. Ebook: $3.99. Paperback: $8.95
This book will guide you through the process of writing a non-fiction book proposal. It lays out the essential information you need to construct a proposal that will address the questions agents and acquisition editors are asking and help you to present the most compelling case you can make for publication. It includes examples from real book proposals and describes the challenges that these writers faced in presenting their strongest argument for publication.
Ask the Agent E-book Now Available For $2.99
Ask the Agent, the e-book, is now available for purchase in both Kindle and epub editions. This book contains the best selections from the Ask the Agent blog as well as new material.
Ask the Agent 