Elizebeth Moon's SF (Vatta's War series and Familias Regnant, which includes the Herris Serano books) are all good. They have a similar flavor to the Honor Harrington books.
Now the Honor Harrington books have the advantage of being freely available:
http://baencd.thefifthimperium.com/ (disk 9 - At All Costs)
Yes - it's legal!
Ace