Kyra Nelson has read a sizeable amount of agent query letters from hopeful authors over her one-and-a-half years of interning for a literary agency (where she still works). She started her blog, Thoughts From the Agent Desk not long ago, on which she posts critiques on queries that are sent to her for public feedback.
I’ve read most of Kyra’s critiques and I think she provides rather useful information. This type of feedback is invaluable for novelists seeking representation. Really, when it comes to your query and manuscript, I think the general rule is: the more feedback, the better.
If you’re looking for help on your query letter, I’d suggest you: (1) draft a query letter and clean it up; (2) read Kyra’s previous critiques and apply what you learn to your current query; (3) then submit your query to Kyra for a critique; and (4) then find even more people to critique your query.
Note: Kyra is particularly into superheroes; do with that what you will.
Anyway, I’ve got some heavy editing of my manuscript to do before I draft my awesome query. Good times.