Snapfish has a great deal. Get 100 4x6 prints FREE with any order! Literally, upload 101 prints to your checkout cart, enter coupon code PRINTSNEW and pay $.09 for your one picture, plus shipping! This deal expires January 27th.
The deal gets even better if you don't already have an account with snapfish. Sign-up for a new account and get an automatic $10 credit to your account! It expires in 5 days.