i highly recommend:
the Honor Harrington series - David Weber
the books with the "posleen" aliens in them (another series) - John Ringo (i think)
"Mutineer's Moon" and it's series - i'm not sure who wrote these, John again perhaps
"The Shiva Option" i'm not sure if this has a series behind it, but it's definitely a good read too - not sure who wrote this one at all, Steven something maybe... i forgot sorry.
those are just a few of my favorite series'. there are many more singletons that are worthy of your time as well and i'll try to post those up when i have the time. there's just so many it's hard to remember them all. I'll have to bring em all down from the attic and dust em off to give you guys more good reading material.
also don't get discouraged by the small print and big (sometimes made up) words, it only adds to the story and sense of accomplishment after you're done... and thirst for more haha.