I was wandering the aisles looking at book covers a few days ago and it hit me how many books are getting female armour right nowadays. Yes, there are still submissive covers and covers with highly impractical armour, but there's also a surprising number of covers with really good female armour.
Here are some examples I found for fantasy. Notice how, though several of the women look sexy, they also look competent and are mostly covered by their armour, which is either metal or leather depending on the book.
And for military SF. Sure, none of them are wearing helmets, but aside from the woman on the cover of Ragnarok (who has a headset and thereby might not get a helmet) it's easy to imagine them putting helmets on before heading off to the fight. Whatever army outfitted these women so practically will have helmets for them too.
I found the military SF covers alternated showing women (and quite often men) in tank tops and in armour. I can't imagine anyone going into battle wearing a tank top, so it's nice to see some properly outfitted women heading off to war.
If you want to see more pictures of good fantasy armour, check out Women Fighters in Reasonable Armor. The guy who runs the site realizes that armour isn't entirely for practical purposes (something Una the Blade points out with regards to the often impractical armour worn by men in ages past). For more information on what goes into making female fantasy armour, here's a post by an armorer.
And for anyone who hasn't seen this yet, because it's awesome, College Humor's "Female Armor Sucks".