The other day (on my to Dominique Ansel Kitchen), I stumbled upon this card shop in the West Village that I'd never even heard of (and, if you know me, you should be well aware that I'm a dominant figure in the greeting-card-store scene*). They've had a storefront since 2005 and surprise, surprise - it's great!
They sell a lot of independently published greeting cards (ie. the best ones), some stationary, wall decor, etc. If you find yourself on Christopher Street, you should definitely stop inside.
*Yes, there is a greeting-card-store scene and no I'm not embarrassed to be in it.