I began making digital cards this year. I usually make a "page" in a custom size such as 4 x 6 and then print them at the local photo shop for 19 cents. Then I attach them to coordinating cardstock. I usually do 5 1/2 x 4 1/4 cards so I keep than in mind while doing the card knowing I will have to trim some off the edges.
I have also done some announcement type photo's, also in 4 x 6 I found that they fit nicely in a A6 envelope, and envelopemall.com has so many cool envelopes to choose from at a reasonable price.
There are a few in
My galleryif you would like to check them out.