suede sleeve
This is like the iPod sleeve,,,but taller so it covers perfectly. Made from Ultrasuede so it's washable.
I just had to post and say that this case from sfbags is great. Just got mine and if you love the sleeve that came with iPod (like I did) and you want the same thing for your iPhone, this is exactly what you're looking for.
2nd best thing to going naked in my opinion.