Shutterfly is offering up 10 FREE Custom Cards & Envelopes when you use promo code JUSTFORYOU at checkout! It's valid on square trim and signature cardstock cards 6×8 flat, 5×7, 5×5, 4×8, 5×7 folded and 5×7 trifold. Note that you will need to pay $5.99 for shipping, which makes each card w/ envelope just $.60 shipped each.
This promo code is valid through October 21st.