Straddle Squats are AMAZING!!! It feels a bit awkward and looks kinda weird, but it works parts of your legs that u didn't know u had!
Use a free-bar (Olympic Bar) with weight plates on both sides. Place the bar on the floor, between your legs. Grab the bar with an underhand (supinated) grip in front of your body with your right hand, and in back of you body with your left. The bar will naturally turn to the right side. Stagger your stance a bit so that your right leg is a bit more forward than your left. Squat for desired reps and switch hand position to work the other leg. You'll also work your arms, shoulders, back, and core with this exercise.... it's amazing!
As for my hams, they were worked as I was doing all my squats, so I did some isolation work for them at the end. My quads need more work than my hams do right now, so I'm putting more emphasis on my quads. I usually split quads and hams, sometimes do them together... it just depends. I agree that I needed to do more ham work, but i was getting tired and spent too much time there as it was... plus, I was getting hungry.... so I skimped on the hams a bit. It's ok tho... I'll kill 'em next time!
Try the straddle squats though... they are awesome!!! I hope I described them well enough!