Have you looked at the Note Cards & Envelopes in the Stampin’ Up! catalog? (see them online) I am completely addicted to these (more ideas on my blog). They’re clean, ready-to-stamp and I don’t even have to find envelopes to match them — they’re in the package!
This card features the Fifth Avenue Floral stamp set (see it online):
Do you love the Elegant Thank You? It’s one of the A La Carte stamps that come singly instead of in a set (see a few online).