Rubbing alcohol, and a small amount of elbow grease really help clean up those grayed scuffed-up areas.
I toyed with the idea of running out to buy a new pair of sneakers before my trip. I don't really need them... it's just that mine were looking a little, well, less than white. I think my next pair will be colorful, but for now, this is what I've got, and I'd just as soon not spend the money before I go. [Plus the whole no-spend January and all... doing good so far!] So, I decided to put the rubbing alcohol secret to the test. Mind you, it didn't make my sneakers new again, but... it did freshen them up -- and that's enough for right now. Less money spent before the trip = more money to take ON the trip. Get it? [Oh, I knew you would my savvy readers!]
The picture below shows a cleaner shoe on the left, and an untouched one on the right. Compare the areas I've pointed to, and perhaps you'll see a clearer difference than in the shots above.
Rubbing alcohol. It's a good thing.