Writing a query letter is never easy, but I've found several useful helps that I wanted to share. Most of you probably know of these, but just in case I ever lose my head, I want a record. ;)
The biggest help was Elana Johnson's blog and her book From the Query to the Call. I stumbled upon her blog about a year ago, and she was just starting a series on writing a good query letter. I found her advice so useful at actually getting words on paper, that I purchased her book (which I still refer back to ALL THE TIME).
With all of Elana's success, she now generously offers her book free to anyone who would like it. Don't let that fool you into thinking it's not useful. Seriously the best $8 I've ever spent---I'd still pay money for it. If you don't have it, go get it post haste. You'll find it on her website under the "Query to the Call" tab.
Another helpful blog is Janet Reid's Query Shark. As a successful and respected agent, she breaks down queries that have been submitted by brave souls and points out what is and isn't working. It's a fascinating study. While you can submit your query, I've found it very useful to simply read through her past posts. You start to get a feel for what a query should be and what you definitely should NOT do. So go, and be enlightened.
The last link I want to share is QueryTracker.net. Not only can you sign up for a free account (they have Premium accounts you can pay for if you want to do more) that will track all the queries and submissions you have sent with the dates and names of the agents or publishers, but they have the Query Tracker Forum as well. You have to request an account for the forum in addition to the QueryTracker.net account, but it is well worth the trouble to do so. Here you can connect with other writers and also receive feedback on your work. They have forums for giving and getting critiques on query letters, the first five pages, as well as the synopsis. They have a forum for any questions you may have about the query process and they have forums for about anything book related you could want.
The forums at AbsoluteWrite.com are similar in nature, and also very useful. (So I lied about querytracker.net being the last link.)
There are many other helpful sites and blogs when it comes to querying (see Matthew Rush's blog The Quintissentially Questionable Query Experiement, for example), these are simply the ones that have been most helpful to me. In the comments, feel free to share sites and blogs that have helped you the most with writing your query.
And best of luck to all of you working on writing a query letter!