See Here is offering 25 free 4×8 photo cards right now when you head over here and use code: cards-36.
There are tons of designs so you can make cards with photos as announcements or thank yous. You can also ditch the photo and add your own text, like an invitation.
You will have to pay shipping of about $2.00 for the cards and they will come with envelopes.
*If your shipping charge is much higher, just reduce the number to 20 cards and it should drop down to $2.49. (Thanks Lucy)