Take a look at this post over at MamaSweat. I'm a fan of Functional Fitness. I'm also a fan of short workouts, because what busy mom has time for a 60+ minute workout every day? Especially when your kids are little, it's hard to find the time for such a workout and the necessary shower afterward.
I like the Primal Fitness promoted at Mark's Daily Apple, too. Call me lazy, but I love a 15-20 minute workout. These days my workouts usually consist of what you see in that MamaSweat Video. Seriously, go watch it. Or stay here and watch it:
Three to four days a week I do something like this plus a few extra exercises with heavy weights. I do more squats with different leg positions and lunges. I spend no more than about 20 minutes and I can feel those muscles all day. In a good way. I'm stronger than I was when I was running 3 miles/3 days a week, and doing FIRM videos the other 2-3 days and wearing myself out.
Bodyweight exercises are simple to do anywhere; obviously you don't need a lot of equipment for this workout. A full laundry basket will suffice for the Dead Lifts!
My great muscles are still covered up by...ahem...curves (shall we say?), but that's a whole different hormonal and emotional issue that we don't need to go into here. But I'll just say that having a strong foundation makes a difference! Its good for building that bone density that starts to decrease in our 30's.
So hop to it!