Klorane Extra Gentle Dry Shampoo With Oat Extract ($16) has been my savior ever since I discovered it about a month ago. It's the perfect solution for when your hair needs a proper washing but you just don't have the time or the energy.
What I love about this product and why I think it stands apart from other dry shampoos is that it feels light on your hair. And since it's odorless, it's not going to overpower your perfume (something you better be wearing if you haven't showered that day)! And since the product is delivered through an environmentally friendly aerosol spray, the powerful mist gives your head really great coverage without having to rub your hands through your hair (which would make it even oilier).
Simply spritz, wait two minutes for it to absorb, and then brush your hair out well. That's all it takes to keep your hair looking fairly fresh throughout the day. The drawback is that it will really only last you one day. After that, my darlings, you're going to have to find the time to shower the good old-fashioned way!