You might also consider hanging out at Baen's Bar
, particularly in the so-called "Slush-pile" forum. That forum IS NOT
the official slush pile for submission to Baen. Rather, it is a forum in which interested fans (and some published authors) will critique your baby within an inch of its life. Many budding authors have found that forum quite useful for tuning up their manuscripts before submission. Read the FAQs before posting, and don't take the comments personally.
You should also be aware that the submission process is extremely slow. Those few publishers who accept unsolicited manuscripts are likely to take several years to produce a response -- and that's fast
as the industry goes! Plan on writing your second (or even second and third) novel while submitting the first.